Rudi Garcia's side have won their last eight games to make Juventus wait for the Serie A title, and have opened the scoring before the break in all of those victories.
Milan are also in fine form, though, having won five matches on the spin, and attempted to frustrate the second-placed hosts, only really threatening once when Kaka burst into the area only to see an 11th-minute shot blocked.
The rest of the goalmouth action was at the other end, with centre-back Dodo blazing over the crossbar from a corner before Adam Ljajic had two shots from inside the penalty box blocked in quick succession.
Francesco Totti tried his luck ambitiously from distance on a few occasions, but never tested Christian Abbiati, who, due to Roma's poor finishing, had yet to make a save when Pjanic beat him on 43 minutes.
The Croatian playmaker collected a quickly-taken free kick from Totti to turn and shoot into the bottom right corner from 15 yards, for his sixth goal of the season and second in four games.
Victory tonight will take Roma to within five points of Juve at the top of the table.