Ten-man Roma held Como to the first goalless draw of the Serie A season after league top scorer Donyell Malen was sent off at the Stadio Giuseppe Sinigaglia on Sunday.
Neither team could find the breakthrough in a clash between two sides widely regarded as dark horses for the title, leaving champions Inter two points clear of Roma in first place following their 3-0 win over Parma on Saturday.
Roma had the better of the first half as Lorenzo Pellegrini, making his first league start in six months, curled a shot off the post after Paulo Dybala's weak finish failed to trouble Jean Butez.
But Malen's reckless lunge eight minutes into the second half proved costly as the Roma striker, who has scored six league goals this season, was shown a straight red card.
An injury to referee Michael Fabbri meant he had to be replaced by fourth official Simone Sozza for the final 20 minutes as Como pushed forward.
However, the home side struggled to pressure Roma's Pierluigi Gollini, who was making his first league appearance for more than two years after an injury to first-choice goalkeeper Mile Svilar.
Gollini palmed over a fizzing Nico Paz shot and did well to charge down another chance for the Argentina international as he claimed a clean sheet to maintain Roma's unbeaten start to the season.
Both sides are in Champions League action on Wednesday, when Roma host Real Madrid at the Stadio Olimpico and Como travel to Feyenoord.
Later, Lazio can go level with leaders Inter when they face Monza in Rome. Lecce host Bologna and Milan go to Sassuolo before surprise package Cagliari welcome Juventus to the Unipol Domus in the late kick-off.