Lazio got the better of its city rival in a thrilling match that saw five goals, including one from the halfway line, and a red card for both sides.
Goals from Antonio Candreva, Miroslav Klose and Stefano Mauri were enough for the home team at Stadio Olimpico despite efforts from Erik Lamela and Miralem Pjanic narrowing the deficit
Daniele De Rossi's straight red card on the stroke of halftime didn't aid Roma's cause as the club suffered defeat for the third time in its last four matches, while Mauri was sent off late on for a second bookable offence.
After a floodlight failure halted the match for around five minutes, Roma took an early lead as Lamela headed in Franceso Totti's corner for his seventh goal in his last six matches for Zdenek Zeman's side.
The Biancocelesti were slightly aggrieved that they were not awarded a free kick in the build-up to the goal, but they almost pulled level almost immediately as Hernanes tested Mauro Goicoechea from distance.
Totti was at the heart of everything Roma was producing, and he forced Federico Marchetti into a smart save as his low shot from the corner of the box was well parried by the goalkeeper.
Klose was back from suspension for the home team, and he posed his first threat as his header was turned away well by Goicoechea, though the referee had already blown for a foul earlier in the move.
Persistent heavy rain was making the playing conditions increasingly difficult and meant the number of chances were much fewer, though Abdoulay Konko went close as his flicked header from Hernanes' free kick went just over the bar.
Lazio was then gifted an equalizer as Candreva's powerful free kick was straight at Goicoechea, but the young Uruguayan could only parry the ball into his own net, though the slippery conditions may have played a part.
Vladimir Petkovic's players had their tails up, and they almost hit Roma on the counterattack as Candreva broke away down the right before finding Klose on the edge of the area, but the Germany international could only fire over.
With three minutes remaining of the first half Lazio did take the lead as Klose turned in Hernanes' low cross-shot for his seventh Serie A strike of the campaign.
Roma's first half went from bad to worse in stoppage time as De Rossi received his marching orders for a slap on Mauri when awaiting a free kick on the edge of the area.
It took Lazio just 90 seconds of the second period to extend the lead as Ivan Piris' weak defensive header fell at the feet of Mauri on the edge of the area and he made no mistake in slotting it past Goicoechea.
Petkovic's team was relentless in its attacking and Goicoechea had to pull of an acrobatic save as Hernanes' shot was heavily deflected to leave the goalkeeper slightly wrong footed.
Roma pushed for an opportunity to get back into the game, but almost fell further behind when Candreva fired a low shot across goal that Goicoechea held onto well.
The Giallorossi should have pulled one back when Pablo Osvaldo found himself free in the box from Totti's corner but he couldn't control his header and saw the ball disappear over the bar.
Hernanes continued to pose a threat from midfield and he almost got himself on the score sheet but his low curling effort from 20 yards was turned around the post by Goicoechea at full stretch.
Zeman's team continued to press and substitute Marquinho threatened with a shot from just outside the box that went narrowly over Marchetti's crossbar.
Mauri received his second yellow card after he was adjudged to have handled on the halfway line, though replays suggested it may have hit his shoulder.
Roma capitalized on the decision as Pjanic scored directly from the free kick as Marchetti was caught off his line and couldn't keep out the speculative effort from all of 50 yards.
The 2001 Serie A winner pushed for a late equalizer and Osvaldo should have provided it as his reached Michael Bradley's searching pass but could only volley wide when clean through on goal.
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