Clayton Donaldson could have won it for Brentford, but sliced wide in the last minute having earlier teed up Harry Forrester for the equaliser after Carl Baker had given the hosts a first-half lead from the penalty spot.
The result saw Brentford slip five points behind second-placed Bournemouth.
But asked if they can still win automatic promotion, Rosler said: "Yes we can but we have to win at Crewe.
"The performance was very good. It was another very good away game and I am very happy.
"We addressed the game differently to when we were at MK Dons. At MK Dons we played very high up and pressed them in their own half, but you can't do that in every game.
"The plan here was to let them come at us and use the pace of Clayton Donaldson. That nearly paid off with the massive chance he had.
"We started very well in the first 20 minutes in terms of performance, playing in their half and creating chances and then the game evened out, they got a little bit more control.
"We totally controlled the second half. They had two shots at goal from outside the box. We had a massive chance to win it late on, but overall I am happy with the performance."