Klopp said: “Long term perfect performance for pretty much 80 minutes or so. We made defensively one mistake.
“The penalty is not a penalty but that is the situation and now it is 5-2. Of course we would have been more happy with 5-0 or 5-1 but 5-2 is a fantastic result. We go there and try again.
We had all these runs behind, it changed the game completely and they couldn’t cope with that. We scored these goals and could have scored more.
“That is all positive, at this moment it doesn’t feel all positive because they scored these two goals but tomorrow I will see the really good part of the game.
“It is absolutely better than I thought before the game but at the moment of course a a little mistake.”
Liverpool captain Jordan Henderson added: “It felt as though we were in full control but we basically gave them two goals, you can’t do that in the Champions League. At the same time we played well, we will go there with a three goal advantage.
Overall we have got to stay positive. We knew it would not be easy tonight, we know it will not be easy there. It will be a challenge but one we will look forward to and one we will hopefully finish them off.
However, it looks like Liverpool will have to do without Alex Oxlade-Chamberlain, who was taken off on a stretcher in the first half.
“Oxlade-Chamberlain is probably a really bad injury,” Klopp said.
“That is bad news for us. The squad doesn’t get bigger at the moment so we need to be creative in the next few games.”
Roma produced an unlikely comeback to beat Barcelona in the quarter-final and manager Eusebio di Francesco hopes history can be repeated.
He said: “We started well, but then we lost our heads a bit. That reaction late on was very welcome, though, and we’ve got to believe in the comeback.”