Vincenzo Montella got the only goal of the game for Roma in the 63rd minute when he was on hand to poke home Hidetoshi Nakata's corner.
With four matches to play, Roma are top on 67 points whilst Lazio have 62 and Juventus, who won at Fiorentina on Friday, have 61.
Lazio fought back twice to level matters at 2-2 in Napoli but had Juan Sebastian Veron sent off for dissent in the 57th minute.
However, down to ten men, the Rome side found the necessary endeavour to keep their championship dreams alive and shocked the home side with two goals to win the game.
Nicola Amoruso had given Napoli the lead in the 24th minute but a cool finish by Hernan Crespo made it 1-1 just eight minutes later.
Both sides came out for the second half fired up and Amoruso made it 2-1 just 60 seconds into the period.
However, with neither side playing well defensively, Crespo replied with his second of the game in the 51st minute, hammering home from inside the area.
After Veron's sending off, it was Czech international Pavel Nedved that got Lazio back in front with a strike mid-way through the second half.
With Napoli desperately trying to get the equaliser, Fabrizio Ravanelli rounded off a great counter-attack to make it 4-2 in the final minute.
Parma slipped up in their quest for a Champions League spot as they slumped to a 2-0 away defeat at relegation-threatened Reggina.
Midfielder Andrea Bernini grabbed the all important opening goal with his first in Serie A, seven minutes from the break as he latched onto a loose ball and smashed home a 30 yard rocket.
Not content with this, Bernini got his second of the game, 14 minutes from time as he struck an emphatic shot into the corner of the net to give the home side a two goal lead.
Bari and Lecce both drew in their battles against relegation, the former 2-2 at home to Vicenza, the latter away at Verona.
Vicenza opened the scoring through Lamberto Zauli in the 46th minute but Gionatha Spinesi got the equaliser from the spot.
Marco Zanchi appeared to have given the visitors the win with a fine header in the 86th minute, only for Spinesi to once again level in the last minute in similar fashion.
Udinese played out an exciting 3-3 draw with Perugia, as the home side fell three behind but fought hard to share the spoils.
Perugia had gone into a seemingly impregnable lead through Marco Materazzi's 20th minute penalty followed by two efforts from Ahn Jung-Hwahn.
Going into the break three down, the team talk woke Udinese up and Roberto Sosa and Roberto Muzzi scored two minutes apart to make it 3-2 in the 57th minute.
However, it seemed like Perugia would take all three points until a controversial last minute penalty allowed Stefano Fiore to equalise.
In the final game on Saturday, Brescia and Bologna battled to a 0-0 draw which helps both sides in their respective fights to stay in the division and gain a Uefa Cup berth.
