Veteran strike duo Heidur Helgusson and Craig Bellamy inspired the Bluebirds to a comfortable win that moved them four points clear at the top of the Championship.
Berg felt the scoreline was somewhat flattering in Cardiff's favour but admitted Rovers had not deserved to take anything out of the match.
"We are disappointed to lose another game at home," said Berg. "We think Cardiff were the better team all over, although maybe not as much as the scoreline suggested but you can't have any complaints.
"They were more experienced than us, they had far better finishing and they also defended better than us - I think that was the key in this game.
"We were not happy with the way we defended - we can defend much better than we did and, also, the way we used the ball in the first half is a little bit of a way off where we want to be.
"We can play better than this."