The victory has kept Rosler's men in fourth place in the League One table.
"The mental strength is fantastic and I think we are better this year than last year. I see improvement," Rosler told BBC London 94.9.
"How we turned it around was fantastic. All three of the substitutes gave us a big lift.
"That is what it is about being a top team - having people on the bench who not only fill gaps but come on and turn the game in our favour."
Brentford lost to Yeovil Town in last season's playoff final.