A 65th-minute opener from defender Mehdi Benatia and a first goal in a Giallorosso shirt for Gervinho earned Roma a victory that takes them clear after Napoli were held at home by Sassuolo.
The hosts ended the game with 10 men when Antonino Barilla earned two late yellow cards to compound the Blucerchiati's woes.
Napoli surrendered their 100 per cent start to the season as Sassuolo claimed their first ever Serie A point from a 1-1 draw at the Stadio San Paolo.
Sassuolo were pointless having conceded 15 goals in four games when arriving in Naples.
Simone Zaza thought he had merely given the Neroverde brief reason to cheer with his 20th-minute response to Blerim Dzemaili's early opener, but on this occasion their luck was in as Napoli ran out of steam.
Juventus needed an own goal from Alessandro Bernardini to come from behind and beat Chievo 2-1 at the Stadio Marc'Antonio Bentegodi.
Cyril Thereau found his way through a sluggish visiting defence to open the scoring before Fabio Quagliarella dragged his colleagues back into the game after the break.
An under-par Bianconeri side were generally short on ideas and were lucky the hapless Bernardini gifted them all three points.
AC Milan plundered two goals at the death in Bologna to rescue a 3-3 draw and deny their hosts a first win of the season.
Andrea Poli's early opener came against the run of play but Diego Laxalt soon hit his first goals in Italian football to give Bologna the half-time lead.
Jonathan Cristaldo then headed home a third to steer the Rossoblu towards a likely victory but a late double salvo from Robinho and Ignazio Abate spoiled the party at the Stadio Renato Dall'Ara.
Milan remain in the bottom half of the table with only five points while Bologna are 16th ahead of Sunday's trip to leaders Roma.
Lazio put last weekend's derby defeat to Roma behind them with a 3-1 triumph over 10-man Catania.
Ederson put the hosts on their way in the sixth minute before Catania midfielder Pablo Barrientos equalised two minutes later.
Senad Lulic then put Lazio in front in the 39th minute.
Catania's hopes of an equaliser got more complicated after defender Giuseppe Bellusci was sent off for a second bookable offence on the hour mark.
Lazio substitute Hernanes killed the game off at the death.
Livorno continued their solid start to the season with a battling 1-1 stalemate against Cagliari at the Stadio Armando Picchi.
Andrea Luci opened the scoring for the hosts midway through the first half but the visitors pulled level thanks to Victor Ibarbo's 53rd minute goal.
Promoted Hellas Verona twice battled from a goal down to earn a share of the spoils against Torino at the Stadio Olimpico.
Alessio Cerci's 36th-minute penalty had put the hosts ahead and, although Juanito equalised a minute before half-time, Cerci's second handed Torino the lead for the second time in the 52nd minute.
However, the visitors were awarded a spot-kick midway through the second half and Jorginho kept his cool to earn Verona a 2-2 draw.
Ten-man Parma struck four times in the opening half on their way to a first win of the season at the expense of Atalanta.
The hosts, who had found the net just twice in their opening four games, made amends in an explosive game which saw six goals scored before half-time.
Atalanta's Giacomo Bonaventura cancelled out Djamel Mesbah's opener in the 20th minute.
Two goals from Marco Parolo and one from Aleandro Rosi handed Parma a 4-1 lead with 10 minutes to go in the half, but German Denis reduced the arrears before the break.
Parma striker Amauri was sent off for dissent early in the second half and, although Atalanta substitute Marko Livaja cut the deficit to 4-3 with 11 minutes remaining, the Gialloblu held on for victory.