"At the final whistle it was a wonderful feeling," Petkovic told Sky Sport Italia.
"We did well to work as a team and were able to interpret the match, even if it meant playing long balls.
"In terms of mentality and effort, we proved all of our quality. We paid for some debatable incidents, such as their goal and Stefano Mauri's red card which I thought was unfair, but we did well to get a positive result anyway."
The victory sees fifth-placed Lazio stretch their lead over Roma to five points.