The Catalan outfit was thrashed 7-0 on aggregate after Bayern added a 3-0 victory at the Camp Nou on Wednesday to their four-goal triumph in Germany last week.
While he is frustrated by his side's slump, Rosell feels that the Munich club are the best in Europe.
"It's a very excessive result compared to what happened over the two legs but Bayern were the better side," said Rosell. "In my opinion, we lost the tie over in Munich and we had too big a deficit to redress the balance here. It was always going to be tough.
"I think that Bayern are currently the strongest team in Europe and that they will win the final, although in football you never know.
"I don't think that Spanish teams did all that badly in the competition this season. Now we must wait for next season and see what happens. I would like to congratulate Bayern because they were clearly better than us and deserve to be in the final."
Barcelona turn their focus to La Liga when they face Real Betis on Sunday.