Roma had already said in April that De Rossi would remain first team coach "for the foreseeable future", with Tuesday's announcement only confirming the three-year extension to the 40-year-old's deal. Former Roma captain De Rossi came in as interim boss when Mourinho was sacked in January.
Roma finished last season sixth in Serie A and outside the Champions League positions, a disappointing end to a season which looked to have turned around once De Rossi took over. However he has shown promise for someone whose only previous managerial job was an ill-fated four months at lower-league outfit SPAL which came to an abrupt end in February last year.
De Rossi, a World Cup winner with Italy in 2006, is an idol for Roma fans as a local boy done good who starred in some of the club's best teams of the last two decades, alongside fellow icon Francesco Totti.