However, just one minute after Watson scored, Revell's header caught out Scott Carson and won the points for the Millers.
Wigan started the game slowly, but Watson missed the best chance for the hosts in the first half when the ball fell loose from a corner and he blazed wide from the middle of the box.
Rotherham's loan players were combining well around the Wigan penalty area, as Lawrence and Emmanuel Ledesma looked particularly threatening, and it took a fine block by James Perch to deny Lawrence when he was through on goal.
However, the former Manchester United player got his goal minutes later when he capitalised on some poor defending to slot the ball past Carson from close range.
Wigan forced an equaliser midway through the second-half as Watson headed home James McClean's cross at the near post, but Revell immediately regained the lead for the visitors with his own header from Ledesma's free kick, and Wigan could not find a reply this time.