That historic victory three years ago remains the sole occasion when United have successfully overturned a first leg deficit in Europe’s top competition, having lost the first leg 2-1 at the Stadio Olimpico.
But as the Red Devils look to repeat that feat, Ferguson has insisted it was a one-off achievement.
"I haven't thought about the Roma game," he said.
"They were probably equal to what Bayern are now in terms of ability and it was one of those performance you hope you could see every week. But you don't.
"It was a once-in-a-lifetime European performance. The scoreline suggests that.
"The thing is to make sure the performance level is good. That makes a difference to the supporters and the players' belief and confidence. From there we can start gathering ourselves again."
Rooney's five goals in six Champions League appearances this season have been crucial in United reaching the latter stages.
