* Roma beat Lazio for first time since March 2011
* Milito celebrates return with two goals for Inter
* Rossi on target again for unbeaten Fiorentina (Adds details)
Sept 22 (Reuters) - AS Roma coach Rudi Garcia succeeded where his three predecessors failed by taking his team to a 2-0 win over arch-rivals Lazio on Sunday and maintaining their 100 percent record in Serie A alongside Napoli who won 2-1 at AC Milan.
Mario Balotelli missed the first penalty of his career after Miguel Britos and Gonzalo Higuain scored early in each half for the visitors whose last away win in the fixture was 27 year ago. Balotelli later scored Milan's consolation and was sent off for arguing with the referee after the final whistle.
Federico Balzaretti and Adem Ljajic, from a penalty, gave Roma their first derby win for 2-1/2 years, while Lazio's misery was complete when substitute Andre Dias was sent off after only three minutes on the pitch.
Carlos Tevez and Fernando Llorente scored in a five-minute spell before halftime to give champions Juventus a 2-1 win over Verona and the Argentine saw another effort hit the post, roll along the line and hit the other upright before bouncing away.
Giuseppe Rossi, sidelined for nearly two years by successive knee ligament injuries, continued his impressive return by scoring his fourth goal of the season in Fiorentina's 2-0 win at Atalanta after Matias Fernandez had put them ahead.
Diego Milito, making his first appearance after a seven-month injury layoff, scored twice after coming on as a second-half substitute as Inter Milan walloped Serie A newcomers Sassuolo 7-0 away.
Milito was one of four Argentines to score, alongside Rodrigo Palacio, Ricky Alvarez and Esteban Cambiasso, in Inter's biggest Serie A win since 1966 when they beat Brescia by the same score. Saphir Taider and an own goal by Raffaele Pucino completed the rout.
Juventus, Fiorentina and Inter, all unbeaten, have 10 points from four games, two behind Roma and Napoli.
Injury-plagued Milan have only four points after starting the season poorly for the second time in a row. Last year, they eventually recovered to finish third with coach Massimiliano Allegri battling constant speculation over his future.
Roma, backed by U.S. investors, splashed out 66 million euros ($89 million) on new signings in the close season, over three times more than Lazio whose fans again protested by entering the Stadio Olimpico after kickoff.
There was little to choose between the sides in the first half, with Gervinho heading wide for Roma in the closest effort.
Germany forward Miroslav Klose nearly put Lazio ahead early in the second half before Roma took control.
Balzaretti struck the post and, in the next move, fired Roma ahead when he met Francesco Totti's chipped cross with an angled left-foot drive at the far post.
Roma captain Totti, starting his 22nd season at the club, was never far from the action and was denied a clear run on goal in the 81st minute when he was barged over by Dias, who was dismissed.
Serbia forward Ljajic made sure of the points for Roma when he won and converted a stoppage time penalty. Totti, the usual penalty taker, missed a chance to score his 10th derby goal as he had just been substituted to a standing ovation.
Roma had failed to win their previous five meetings against Lazio, during which Luis Henrique, Zdenek Zeman and Aurelio Andreazzoli all occupied the hot seat.
Injury-plagued Milan were quickly in trouble as Britos put Napoli ahead in the sixth minute and it got worse with Higuain, signed from Real Madrid in the close season, scored his third league goal for Napoli early in the second half.
Balotelli, who had converted the previous 21 penalties he has taken in official matches, saw his spot kick saved by Pepe Reina just after the hour.
He also hit the crossbar, had another penalty appeal turned down and saw a dipping shot turned over by Reina before curling in a consolation in stoppage time.
Already booked, Balotelli completed his evening by arguing with the referee after the final whistle and was shown a second yellow card. ($1 = 0.7402 euros) (Writing by Brian Homewood in Berne; Editing by John Mehaffey)