A win would have lifted the home side, who remain unbeaten in Serie A this season, above league leaders Juventus.
The club's coach told La Gazzetta dello Sport: "We did well against Cagliari. The important thing is that when we don't win, we don't concede goals and hence, we don't lose.
"We played a good match and we didn't get three points because [Cagliari goalkeeper Vlada] Avramov had a fantastic game. Our main problem has been that some of our players are not at the same physical level as others.
"When there is an international break, there tends to be a drop in form when returning to the competition and that affects the performance of the team."
The results leaves Roma second in the table, while Cagliari are 14th.