Two howlers from the German goalkeeper saw Liverpool lose 3-1 in Kiev.
But Robertson told the Liverpool Echo: "We win as a team, we lose as a team.
"Of course he (Karius) made mistakes but we are not blaming him.
"He will hold his hands up. He has been incredible since he go the No 1 jersey. He is young and he will learn from it. He will be a top, top keeper.
"We have fallen short and there are no words that we can say to Loz that will make it better for him.
"We went around him. We all gave him a hug and tried to lift him. I don't think anyone thought that was going to happen."