Roma inflicted Parma's first loss of the season to move into second place on 14 points, two behind champions Juve and Milan.
On Saturday, Juventus won 3-2 at Ancona and Inter Milan drew 2-2 at Brescia, which prompted Inter to replace Argentine coach Hector Cuper with former Milan boss Alberto Zaccheroni.
A 37th minute goal from Andrea Pirlo won an entertaining encounter for Milan after Carlo Ancelotti's side suffered some early pressure from Lazio.
The visitors thought they had taken the lead in the 17th minute when Dejan Stankovic turned in a pass from Bernardo Corradi but the goal was ruled out for offside -- a decision that appeared harsh on the television replay.
Milan's goal came when Cafu's fierce shot was parried by Angelo Peruzzi, the Lazio defence failed to clear and, after Filippo Inzaghi's shot was blocked, Pirlo pounced.
Lazio played attractive football, though, and might have equalised had Claudio Lopez made the most of an error by Pirlo in the 61st minute, firing straight at Dida after the Milan midfielder had given the ball away on the edge of the area.
As the game went on a second goal for Milan, inspired by Gennaro Gattuso, looked more likely than a Lazio equaliser and it almost came when Andriy Shevchenko hit the post two minutes from time after being set up by the lively Brazilian Kaka.
ROMA'S BEST
Unbeaten Roma look back to their best this season and underlined their re-emergence
Argentine defender Walter Samuel put Roma ahead in the 29th minute with a left foot finish after a skilful run and cross from the left by highly promising midfielder Daniele De Rossi.
Antonio Cassano, another exciting Roma youngster, made it 2-0 on the hour with a header at the back post after more excellent work from De Rossi.
The source of much of Roma's creative play was Italy's Francesco Totti and he went close to a third when his long-range shot was tipped on to the bar by goalkeeper Sebastien Frey.
"We produced a great performance today because it is never easy against Parma. We were well organised, attentive and moved well with the ball," said Roma coach Fabio Capello.
"We took a big step forward today on a number of levels and showed a real desire," he added.
It was a topsy-turvy day for Bologna striker Fausto Rossini, whose headed own goal after 48 minutes put his side behind at home to Perugia.
The visitors added a second in the 69th minute when English striker Jay Bothroyd tapped home after a dreadful mix-up in the Bologna defence.
But former Chelsea midfielder Samuele Dalla Bona pulled one back for Bologna in the 71st minute before Rossini made amends for his earlier blunder with the equaliser -- a smart back-heel to turn in a Fabio Pecchia shot.
