The French coach was sent to the stands with 17 minutes to go after a touchline confrontation with the match official Domenico Celio
The French coach was sent to the stands in the 73rd minute of the game in the Italian capital after a heated conversation with match official Domenico Celio - but insisted afterwards that he was not sure what he had done wrong.
"It was the referee's decision - I don't want to speak about it," Garcia told Sky Sport Italia.
"But after the game I went to talk to the referee to understand why I had been sent off. He told me that I had blown up. Maybe I live the game too much!"
Garcia did admit that he had been frustrated by his side's failure to turn their dominance into goals, as the Giallorossi failed to reclaim top spot in Serie A from Juventus by being held to a draw for the third consecutive game.
However, despite the setback, the ex-Lille boss insisted that Roma still have every reason to be feeling upbeat, particularly as third-placed Napoli were beaten at home by Parma on Saturday.
"This 0-0 is a random result. We played a great first half. It was a shame we didn't manage to go ahead," he mused.
"One important thing is that when we do not win, at least we do not lose. We didn't manage to score a goal but the man of the match was [Cagliar goalkeeper Vlada] Avramov.
"Our problem is that some players are in different physical condition from the others.
"But the glass is still half full. We have earned a point on third place. And we will do everything to return to the summit."
Roma, who now sit one point behind Juventus, return to action against Atalanta in Bergamo next weekend.