The 30-year-old is upset that his side were not awarded penalties in recent games and has said that league leaders Juventus are getting lucky with a number of decisions.
"We don't feel damaged by referees. However, against Torino - the foul on [Miralem] Pjanic - and in Atalanta, there were two clear penalties not granted in our favour," he told Roma Channel.
"Juve, however, have got a bit lucky with referees, and have had favourable moments. I think of the games against Chievo and Tonio in particular.
"They say that at the end of the season these wrongs balance out, and we expect this to occur."
Roma are currently second in the Serie A table, three points behind Juventus.