The Dutch star, who scored two goals as he captained Juup Heynckes's side on the night, said that the game was more difficult than it appeared.
"Four-nil sounds easy but it was tough," admitted Robben.
"I'm proud of the lads. We worked very hard."
A further brace from Claudio Pizarro was enough to send Bayern through to the last 16 of the DFB-Pokal.