The Bees face a home replay against Southend next Tuesday after the teams drew 2-2 at Roots Hall over the weekend.
Rosler's troops have found the League Two Shrimpers tricky customers this season, having been beaten by them in the Johnstone's Paint Trophy in December.
And the League One high-flyers were pegged back by two goals from striker Barry Corr after taking a 2-0 lead on Saturday.
The reward for Brentford winning the replay would be a dream home derby with their illustrious west London neighbours, and the cup holders, at the end of January.
"We have to do it the hard way," said Rosler after the game.
"Southend are a good side. They play football that is not easy to cope with.
"The two strikers were a handful and Gavin Tomlin caused us all sorts of problems. Tomlin is an excellent player."