With Inter Milan being held to a disappointing 1-1 draw at home to Genoa earlier on Saturday day, the capital club took full advantage and Hernanes' strike on the half hour was enough to beat the team bossed by former Lazio coach Delio Rossi.
The Biancocelesti are now eight points behind pace-setters Juventus.
Inter lost further ground on their rivals although they were grateful for a point in the end as Esteban Cambiasso's strike five minutes from time cancelled out Ciro Immobile's 77th-minute effort.
There was still time for the strugglers to spurn a golden opportunity in the last minute as Marko Livaja somehow hit the woodwork from a yard out.
Andrea Stramaccioni's men were also leapfrogged on goal difference by Fiorentina, who finished the year in the Champions League places with a comfortable 3-0 victory at lowly Palermo.
Stevan Jovetic had been a doubt for the game due to a thigh injury but opened the scoring in the 50th minute and then doubled his side's lead with a penalty seven minutes from time.
Jovetic might have been celebrating a hat-trick in the final minute after Fiorentina had won another penalty, but centre-back Gonzalo Rodriguez took over spot-kick duties and confidently converted.
Two late goals saw Napoli end a chastening week with a flourish following a 2-0 triumph at 10-man Siena.
The Italian Football Federation (FIGC) this week deducted two points from Napoli for a former player's involvement in match-fixing, while they then exited the Coppa Italia courtesy of a second home loss to Bologna in three days.
Christian Maggio broke the deadlock on Saturday in the 86th minute, while Edison Cavani netted immediately after from the spot, while Siena's afternoon was compounded in added time when Emanuele Calaio was sent off after needlessly elbowing Valeron Behrani.
Goals from Jaime Valdes and Nicola Sansone helped Parma moved up to eighth after coming from behind to claim a 2-1 away win over Bologna, who took the lead through Frederik Sorensen.
Torino pulled clear of the relegation zone as a Gennaro Sardo own goal and a Alessandro Gazzi strike secured a 2-0 home victory against Chievo.
Atalanta striker German Denis struck from the penalty spot to cancel out Muriel's opener for Udinese as the mid-table teams shared a 1-1 draw.
In Saturday's late kick-off, a brace from Erik Lamela inspired Roma to a 4-2 home victory over AC Milan at the Stadio Olimpico.
Nicolas Burdisso broke the deadlock in the 13th minute with Pablo Osvaldo doubling Roma's lead 10 minutes later.
Lamela's double ensured there was no way back for the visitors, who at least grabbed late consolations through Giampaolo Pazzini and Bojan Krkic after Marquinho was sent off for Roma.
Meanwhile on Friday, Juventus moved 10 points clear at the top of Serie A as a 3-1 win at Cagliari to set a new league record of 94 points in a calendar year.
Juve had to come from behind after Mauricio Pinilla put the struggling Sardinians in front in the 16th minute, but a brace from Alessandro Matri, after Arturo Vidal had missed a penalty, turned the game around.
Mirko Vucinic added a third deep into stoppage time, while Cagliari ended the game with 10 men with Davide Astori picking up two yellow cards.
The win extended Juve's advantage over second-placed Inter Milan and Lazio in third, although both have a game in hand.
In Friday night's other game, Pescara scored a stoppage-time winner to move out of the relegation zone with a 2-1 success over Catania.
Eugenio Togni netted his first ever Serie A goal with the last kick of the game
Mervan Celik earlier gave Pescara a 23rd-minute lead, but Pablo Barrientos levelled soon after.
Satuday's Serie A Fixtures
Friday's Serie A Fixtures