Roma's Bosnia midfielder Pjanic skipped past three players before calmly firing home two minutes from the break and Ivorian Gervinho tapped in the second goal at the end of a lightning-quick counter attack after 65 minutes to down sorry Milan.
"Pjanic scored an incredible goal today, it's the sort of thing you see once in your life," said Adem Ljajic, who was involved in the brilliant build-up to Gervinho's goal.
"It (the title) doesn't depend on us, but if we play like we did tonight then we can beat anyone."
Rudi Garcia's Roma team, beautifully conducted by 24-year-old Pjanic, recovered from a slow start to play exhilarating football and are now on a club record 85 points after winning their 26th match this season, also a record for the Rome outfit.
If Antonio Conte's Juventus side win on Monday to reclaim an eight-point lead with three games left to play, their third title in a row will be little more than a formality.
Milan's comprehensive defeat brought a five-match winning streak to an end and is a dent in their hopes of securing a place in the Europa League for next season.
Clarence Seedorf's side stay seventh, level on 51 points behind Parma, who visit Cagliari on Sunday (1300 GMT), and five adrift of fifth-placed Inter Milan before their rivals host third-placed Napoli, who have 68 points, on Saturday (1845 GMT).
Milan began the match the stronger side but could not create anything against a Roma defence missing lynchpin Mehdi Benatia, with visiting striker Mario Balotelli offering little threat.
The home team initially played well below their usual vibrant standards but as the first half wore on they began to impose themselves play on Milan.
Something special was needed to break the deadlock and forward Ljajic almost provided it in the 26th minute, his neat footwork in the area leading to a close-range shot stopped by a brilliant sliding block from Milan defender Adil Rami.
Pjanic went one better just before the break, however, when he stunned the Olympic Stadium with an incredible solo effort that will be a strong contender for goal of the season.
Picking the ball up in midfield, he set off towards goal, slaloming past Sulley Muntari and Riccardo Montolivo before finally slipping round Rami and confidently rolling his sixth goal of the season past Milan keeper Christian Abbiati.
A team effort was behind Roma doubling their lead, with a rapid passing move sweeping the hosts up the pitch and leading to Ljajic slipping in Francesco Totti.
The Roma captain thumped a shot at Abbiati who spilled the ball to Gervinho and the Ivory Coast striker knocked in the second goal that, despite a late Milan rally, capped a victory that provides a glimmer of hope for their title ambitions.
- Sports & Recreation
- Inter Milan
- Adem Ljajic