Tommaso Rocchi gave Lazio an early lead and the derby rivals should have gone ahead further after half time when Aleksandr Kolarov was brought down by Mario Cassatti in a very debatable penalty call. But Sergio Floccari muffed the chance as he shot it straight at Julio Sergio.
However, minutes later it was Kolarov bringing down Simone Taddei in the box and Mirko Vucinic made no mistake with the spotkick. Roma then sealed victory with Vucinic lashing in a free kick for his brace.
The win leaves Roma one point ahead of Inter. AC Milan dropped even further down with their loss against Sampdoria and with it their fading chances at the Scudetto.