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."
Ferguson will be looking to defeat a German side over two legs for the first time in his career at Old Trafford, having previously failed to get the better of Bayern, Borussia Dortmund and Bayer Leverkusen.
If he does so he will take the Red Devils to a third consecutive Champions League semi-final for the first time in their history.
The reigning English champions have won nine of their last 10 home games in knock-out competitions, but victory on Wednesday will - in all likelihood - have to come without the aid of top-scorer Wayne Rooney.
Rooney's five goals in six Champions League appearances this season have been crucial in United reaching the latter stages.
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