Rudi Garcia’s men began the season with 10 straight wins but have now been held to a trio of draws in succession and sit one point behind Juventus.
Cagliari goalkeeper Vlada Avramov was chiefly responsible for ensuring Roma were unable to score on Monday evening, the 34-year-old pulling off a number of fine saves.
However, Cagliari had sporadic opportunities of their own and even found the net in the second half through Marco Sau, only for the goal to be correctly ruled out for offside.
Gervinho and Maicon tested Avramov inside the first five minutes as Roma started brightly.
Alessandro Florenzi should have done better when firing over from 20 yards and Miralem Pjanic dragged an effort narrowly wide before the hosts survived a significant scare in the 33rd minute.
Victor Ibarbo's header appeared destined for goal, but Morgan De Sanctis sprung to his left to pull off a terrific reaction stop.
Roma responded impressively, with Gervinho heading firmly against Avramov’s right-hand post and Kevin Strootman forcing the goalkeeper into further action from close range.
Avramov was busy again early in the second half, keeping out a volley from Florenzi before Mehdi Benatia made a mess of the follow-up.
Maicon then tried his luck with a powerful effort towards the top-left corner and the impressive Avramov was again equal to the task.
Cagliari looked to have taken a shock lead in the 54th minute, but the linesman's flag cut short their celebrations after Sau had headed home.
Roma were soon back on the front foot but their frustration was epitomised by coach Garcia being sent to the stands following a disagreement with the match officials.
The visitors retained an occasional attacking threat and De Sanctis had to be alert when pushing away Sebastian Eriksson's long-range effort.
Yet, after Benatia had been forced off through injury, it was Avramov who fittingly had the final say in stoppage time.
A header from Adem Ljajic was helped towards goal by substitute Nicolas Burdisso but Cagliari's keeper got down well to tip the ball around the post.
