After a winner couldn't be found in extra time, the contest went to penalties and despite holding an early advantage in the shootout, Adam Collin saved from Mathieu Baudry and Chris Dagnall to earn the Millers a place in the second tier of English football.
Read below to see how the action unfolded in North London.
2.01pmHello, and welcome to Sports Mole's coverage of the League One playoff final between Leyton Orient and Rotherham United.
2.03pmAfter Queens Park Rangers defeated Derby County in incredible circumstances yesterday, will we see a repeat of the drama at Wembley this afternoon? Let's hope so, although I hope we get a bit more goalmouth action!
2.06pmPlayoff finals are always too close to call with any confidence, but this one really couldn't be any closer if the form in the regular league campaign is anything to go by. Both teams recorded the same number of points during their 46 games, with Leyton Orient's goal difference giving them the upper hand over the Millers.
2.08pmThe two starting lineups are in from Wembley. Full details coming up shortly.
2.13pmROTHERHAM UNITED XI: Collin, Tavernier, Morgan, Arnason, Skarz, Agard, Smallwood, Frecklington, Pringle, Revell, Thomas
2.16pmUnsurprisingly, both managers have named the same starting lineup that began the second leg of their respective semi-final ties. There was a slight doubt over Orient's Dean Cox after he suffered a groin problem 12 days ago, but he has recovered to retain his place in the team.
2.19pmIf you haven't been fortunate enough to see inside the changing rooms at Wembley before, here is your chance. They are a bit of a step up from what Orient and Rotherham are used to experienced in League One!
2.24pmIf Leyton Orient are victorious this afternoon, they will end a 32-year wait to get back up to the second tier of English football. However, Rotherham's last experience of came in 2005, so they are no strangers to that level of football, but the Millers have found themselves having to contend with administrations, points deductions and relegations before earning another shot at promotion to the Championship.
2.31pmPREVIOUS FIXTURES! The first fixture between these two sides earlier in the season came all the way back in October when Leyton Orient edged to a 1-0 victory thanks to a goal from Kevin Lisbie. However, Rotherham earned revenge in the second encounter when Alex Revell scored in the final minutes to give the Millers a 2-1 success.
2.37pmLEYTON ORIENT KEY MAN! Orient have relied on several players throughout the course of the season, but the inclusion of Dean Cox could prove vital to his side's chances this afternoon. The former Brighton & Hove Albion winger is a constant threat to the opposition with his direct approach, while his deliver from set pieces could prove key. Cox has netted 16 goals from 55 appearances this campaign, and if he can add to that tally or provide another assist, Orient could be celebrating promotion at 5pm.
2.41pmROTHERHAM UNITED KEY MAN! Many Rotherham supporters would have feared the worst when Kieran Agard was ruled out of the first leg of the semi-finals, but the 24-year-old returned for the second match to net his 26th goal of the season to help the Millers into the final. The Yorkshire outfit offer an attacking threat from all over the pitch, but the full recovery of Agard is key for their ambitions this afternoon.
2.43pmThere are just over 15 minutes left until kickoff at Wembley. Time for a pre-match prediction...
2.46pmPREDICTION! As I mentioned before, there is nothing separating the two sides in terms of statistics and previous results against each other. However, after a strong end to the campaign, Rotherham deserve to be marginal favourites for this match, and if they can continue their form in front of goal, I think they will just get the better of the O's in a high-scoring final. 3-2 to Rotherham.
2.47pmThe Leyton Orient players have just completed their warmup. The two teams will be ready to come out in just a few minutes!
3 minThe Millers have started very much on the front foot, and it has forced Orient into a couple of panicky clearances. Romain Vincelot concedes a free kick around 30 yards out, but the ball into the box from Ben Pringle is well defended by Orient.
4 minShould Rotherham have had a penalty? I think that they should. A pass was floated into the Orient area for Alex Revell, but he is shoved out of the way by Nathan Clarke. There are big appeals from Rotherham, but the referee remains unmoved.
7 minLeyton Orient have began to settle more into the game now, but Rotherham are still having the bulk of possession. There is a real openness to the contest too, which should bode well for the rest of the match.
9 minCHANCE! Wes Thomas should have done better there. A free kick was sent into the box for Craig Morgan to head into the path of the striker, but despite being just six yards out, he could only divert the ball straight at Jamie Jones.
12 minSHOT! Lee Frecklington does well to get in front of his marker before getting a shot in on goal. However, his effort is weak and straight at Jamie Jones. Steve Evans will be delighted with his side's start.
13 minLeyton Orient are really struggling in defence. They aren't dealing with the long balls that are being punted into the box, and unless they improve, Rotherham will take one of their opportunities. On this occasion, Alex Revell managed to head the ball across the penalty area but two of his teammates failed to get on the end of his knock down.
16 minSHOT! James Tavernier is the next man to try his luck for Rotherham, but like his team's earlier efforts, his strike from 25 yards was comfortably dealt with by Jamie Jones.
20 minLeyton Orient hit the back of the net on 85 occasions during their 46 league games, but they have barely been in the Rotherham final third during these opening 20 minutes. David Mooney is being forced to drop back into midfield, and it's leaving Kevin Lisbie isolated in attack.
22 minOrient finally have some joy after winning a free kick on the left-hand side of the penalty area, but Dean Cox's cross is deflected into the air, and Kevin Lisbie can do nothing with his header from 12 yards.
24 minJames Tavernier lets fly with another ambitious effort from distance but his shot trickles wide of the post. Plenty of intent from the Newcastle United loanee though.
28 minWhile there is plenty of passing in the middle third of the pitch, it's almost non-existent in and around each penalty area. The long balls into the box is becoming slightly predictable, especially in Rotherham's case, and chances inside the penalty box are at a minimum.
30 minSHOT! Just as I speak, another long ball is pumped into the penalty area, and after it finds Orient's David Mooney, the striker tries an instinctive volley from an acute angle, but he can only find the side netting.
31 minBOOKING! Leyton Orient's Scott Cuthbert is the first man into the referee's book after scything down Ben Pringle on the halfway line.
34 minGOAL! Leyton Orient 1-0 Rotherham United (Odubajo)
34 minOrient take the lead from a stunning strike from Moses Odubajo! Again, another ball was floated into the area from a set piece, but after it was only half-cleared by the Rotherham defence, Moses Odubajo chested the ball down on the edge of the area before volleying the ball into the roof of the net from 20 yards!
38 minThat goal came completely out of the blue. It hasn't been the type of game where you would expect a superb individual effort to open the scoring, but the goal from Odubajo was just that. It flew past Adam Collin in the Rotherham goal.
39 minGOAL! Leyton Orient 2-0 Rotherham United (Cox)
39 minLeyton Orient are in dreamland! Two goals in the space of five minutes has completely altered the course of this match. This time, Moses Odubajo turned creator to drill a cross to the back post for Dean Cox to tap into an empty net from three yards.
41 minOrient nearly score a third! A corner was swung in by Dean Cox, but Mathieu Baudry could only head over the crossbar from eight yards. Rotherham need half time.
44 minDean Cox breaks forward for Orient but he is quickly outnumbered and opts to retreat. The transformation of Orient has been startling. They hardly had a kick in the opening 20 minutes, but they have been rampant since the midway point of the half.
45+1 minSHOT! What an effort from Ben Pringle! The ball dropped invitingly for the Rotherham midfielder from around 30 yards out and his dipping effort landed on the top of Jamie Jones's net.
45+2 minHALF TIME: Leyton Orient 2-0 Rotherham United
3.49pmThe half-time whistle goes at Wembley and Leyton Orient are 45 minutes from the Championship after opening up a 2-0 advantage over Rotherham United. The Millers dominated the opening exchanges, but after preventing their opponents from scoring an early goal, Orient fought back brilliantly during the final 20 minutes of the half and they deservedly lead at the break.
3.54pmIn terms of possession and shots on goals, Rotherham have had the better of it, but Orient's two efforts on target have resulted in goals. Most of the credit deserves to go to Moses Odubajo, who has lit up this final with a fantastic volley from distance and drilled cross from the right for Dean Cox's goal. Can Rotherham do anything to turn this around?
3.59pmRussell Slade will be ecstatic with that first half, but he will be drumming into his players that they can't afford to get complacent. Rotherham have shown on several occasions this season that they can turn matches around, and they are sure to come out firing after the break.
47 minDavid Mooney goes down in the penalty area after being tugged back by a defender, but the referee decides that there wasn't enough contact for the striker to have hit the deck.
50 minAlex Revell wins a free kick after being brought down at Mathieu Baudry. Ben Pringle and James Tavernier are lining up the ball around 25 yards from goal. Can they halve the deficit? Tavernier comes close, but his shot ends up on the top of the net.
53 minRotherham get another opportunity after winning a free kick from a similar distance to the last effort. It looks like being Ben Pringle on this occasion. Can he do better than Tavernier? No - he does exactly the same as his teammate! The ball clips the top of the net and goes behind.
54 minSUBSTITUTION! Rotherham boss Steve Evans makes his first change of the match, bringing on Richard Brindley for Wes Thomas.
55 minGOAL! Leyton Orient 2-1 Rotherham United (Revell)
55 minGame on! A free kick into the area causes mayhem and after Jamie Jones fails to deal with the cross, the ball falls to Alex Revell to prod the ball into an empty net from six yards.
58 minSteve Evans is going berserk on the touchline. He is trying to get his team really pumped for this, but I don't think they need much help - they are by far the better team now.
60 minGOAL! Leyton Orient 2-2 Rotherham United (Revell)
60 minINCREDIBLE! Alex Revell lights up this final with an effort that surpasses the goal scored by Moses Adubajo! The ball fell invitingly for him around 30 yards from goal, but after taking a touch, he unleashed a volley that flew over Jamie Jones and into the corner! What a game!
63 minThis has been a remarkable turnaround. Leyton Orient had full control of this contest but they are on the back foot. Alex Revell is playing like a man possessed against his former club.
67 minThe momentum continues to be with Rotherham who are taking every opportunity to pressurise a shaky Leyton Orient backline. Russell Slade must be contemplating making a change. They need to restore a bit of calmness to their play.
71 minRussell Slade and Orient want a foul given against Kari Arnason after he pulled down Kevin Lisbie when through on goal but the Rotherham defender gets away with it. 19 minutes to go.
74 minSUBSTITUTION! Dean Cox is making his exit from the game as Russell Slade decides to bring Shaun Batt on. This is his 31st appearance from the bench this season!
77 minSUBSTITUTIONS! Russell Slade wastes little time in making a second change. Chris Dagnall has been introduced into the action in place of Kevin Lisbie. Rotherham also make an alteration, bringing on Robert Milsom for Joe Skarz.
78 minHow haven't Orient taken the lead! Lloyd James whipped in a delightful cross from the right, but not one of three teammates could put the finishing touches in the six-yard box!
83 minCHANCE! The ball runs through to Kieran Agard around 25 yards out, but he can't gain full control of the ball and his volley is sent skywards. Seven minutes to go. We need a goal or else we are heading to extra time.
86 minBOOKING! That's as cynical as you can possibly get from Ben Pringle, who hacks down Shaun Batt with the winger in full flow down the right.
90 minCHANCE! Lee Frecklington gets in down the right-hand side but his cross to the near post is headed wide by Kieran Agard. He should have done better from six yards out. There will be five minutes of added-on time.
90+3 minOrient win a corner on the right. Is this their moment? No. The first cross is cleared, while the second delivery fails to beat the first man. But they win another!
90+4 minDavid Mooney sees a shot blocked and they get a third corner in quick succession, but it's poor and cleared at the near post. I think we are heading to extra time.
90+5 minFULL TIME: Leyton Orient 2-2 Rotherham United
4.55pmThe full-time whistle goes at Wembley Stadium, and we are going to have 30 minutes of extra time. Can someone find a winner, or will we be heading to penalties?
91 minLeyton Orient get us underway for the start of extra time.
93 minThe O's have started this extra period by penning Rotherham back on their own 18-yard line, but Chris Dagnall can't make the most of an opening.
95 minCLOSE! Oh my. Scott Cuthbert nearly powers the ball into his own net but Jamie Jones pulls off a miraculous stop from point-blank range. Up the other end, David Mooney tries to chip Adam Collin from 20 yards but the ball drifts marginally over.
99 minThis hasn't been your usual nervy extra period. Both teams are pushing men forward to try to get a decisive goal. I wouldn't fancy taking a spot kick in a penalty shootout after playing at such a pace for 120 minutes.
102 minAdam Revell looks like he is really struggling for Rotherham. He could be withdrawn during the short break coming up.
104 minShaun Batt holds the ball up on the byline and draws the foul out of Ben Pringle. Lloyd James curls the ball in, but Nathan Clarke can't head the ball on target from six yards.
105 minSUBSTITUTION! Steve Evans isn't waiting until the break. Alex Revell departs for Haris Vuckic.
105+1 minHALF TIME: Leyton Orient 2-2 Rotherham United
106 minRotherham get us started again. 15 minutes to go - the tension is rising...
108 minThe Millers enjoy a sustained spell of possession, but they lose the ball cheaply in midfield. However, Orient do little on the break and Rotherham have the ball again.
111 min10 minutes to go at Wembley. There are some tired legs out there now! Leyton Orient have dominated possession over the past couple of minutes but they lose the ball without threatening a goal.
113 minA long throw from Nathan Clarke causes confusion in the Rotherham penalty area, but the Millers somehow managed to clear the ball after Lloyd James had seen his goal-bound shot blocked.
116 minMuch of Orient's play is going through Shaun Batt but Rotherham are doing a good job of nullifying the threat offered by the substitute.
119 minOrient are pressing men forward and Mathieu Baudry sees a curling effort blocked by a defender. Clarke sends another ball into the box but Adam Collin comes and claims. I think that could be that.
120 minFULL TIME: Leyton Orient 2-2 Rotherham United
5.36pmEach and every player are physically and mentally exhausted. It's been a superb effort from both teams - it's just a shame that one of them is going to go home without reward.
5.38pmIt looks like it is going to be Rotherham to take first.
5.39pmLeyton Orient 0-1 Rotherham United Kieran Agard gets Rotherham up and running with a confident penalty down the middle.
5.40pmLeyton Orient 1-1 Rotherham United Lloyd James responds by powering his spot kick to the left.
5.40pmLeyton Orient 1-1 Rotherham United Save! Jamie Jones makes a great save from Lee Frecklington. Advantage to Orient.
5.41pmLeyton Orient 2-1 Rotherham United John Lundstram sends the goalkeeper the wrong way with a terrific effort into the top corner.
5.41pmLeyton Orient 2-2 Rotherham United Ben Pringle gets Rotherham back on level terms.
5.42pmLeyton Orient 3-2 Rotherham United Leyton Orient captain Nathan Clarke steps up to slot home his kick into the bottom corner.
5.42pmLeyton Orient 3-3 Rotherham United What a penalty from James Tavernier. He drills his shot into the top corner.
5.43pmLeyton Orient 3-3 Rotherham United Mathieu Baudry misses! Adam Collin makes a comfortable save to his left. We are effectively into sudden-death.
5.44pmLeyton Orient 3-4 Rotherham United Smallwood sends Jamie Jones the wrong way and Chris Dagnall must score for Orient.
5.44pmLeyton Orient 3-4 Rotherham United Chris Dagnall sees his shot saved by Adam Collin. Rotherham are going up!
5.45pmROTHERHAM UNITED EARN PROMOTION TO THE CHAMPIONSHIP!
5.46pmIt's jubilation for Rotherham but it's absolute heartbreak for Leyton Orient. They were two kicks away from promotion, but misses from Mathieu Baudry and Chris Dagnall have cost them dear.
5.49pmThe two finals over the past 24 hours have proven that this format can be memorable for the winners but devastating for the losers. Derby and Leyton Orient have been the better sides in each match but they have fallen at the final hurdle.
5.51pmThat will be all from Sports Mole for this match. What an afternoon! Congratulations to Rotherham United - Steve Evans has done a remarkable job at the New York Stadium to secure the club back-to-back promotions. See you tomorrow for the League Two final between Burton Albion and Fleetwood Town!