Lionel Messi struck on 86 minutes for the only goal of the game.
Roberto said, “They pressed us a lot, we knew that here in front of their fans they would push us and that's how it was. We lost a couple of balls and they had some clear chances.
“We suffered a bit but in games like this is where leagues are (won). There's a long way to go and many teams who will be there until the end."
On the performance of goalkeeper Marc-Andre ter Stegen, he added: “In the end the work is the whole team's. Marc made a couple of great saves and Messi decided the game, but it's a team victory."