The holding midfielder feels his side should have done better after clawing their way back into the match and has called for improvement ahead of the Real Sociedad clash
Rolfes levelled the scoring for Leverkusen in the second half after Wayne Rooney put the hosts ahead, but the Bundesliga side then conceded twice within the space of 10 minutes as they went on to lose the match 4-2.
The midfielder believes his side contributed to their own downfall at Old Trafford after making a number of errors throughout the encounter, specifically when a defensive mix-up allowed Rooney a simple finish to kill off the game late on.
"It was too easy for them. We lost 4-2 and the United goals were a bit unlucky for us. We are not happy with the result and can improve a lot in our play," Rolfes told the official Uefa website.
"The positive is we scored twice; it is not so easy here in Manchester to do that. Perhaps in the game against them in Leverkusen it'll be better.
"If you want to win here or get a draw, a lot of things have to be perfect and it wasn't like that. After the third goal the game was done."
The midfielder then looked ahead to his side's next Champions League game against Real Sociedad and stressed that Leverkusen must have confidence in their own game at the BayArena.
"Real Sociedad are a good team but we have to win at home; we have to play with more confidence and possession," the 31-year-old added.
"Our style of play is to have more of the ball and not just defend like today. United did well: they were aggressive and well organised, but we knew that already."