I think we can't compare Mourinho and De Rossi at the moment, although mourinho was sacked because he was considered unsuccessful at Roma but although I think for now De Rossi can go in a better direction because of all Mourinho legacy in Rome, besides that I think Mourinho has more advantages because he is more senior than De Rossi in coaching a team so far, So it is better for us to see how much De Rossi is capable of bringing Roma this season than we have to keep remember about what Mourinho has given for Roma so far.
Even though Mourinho is a failed, at least he has given Roma the UEFA conference league trophy. Of course i know it is UEFA's lowest level competition trophy, but become a champion is still a title which is a part of success achieved by coaches and players. Mourinho failed to fix AS Roma in Serie A, but Mourinho has written his name in the history of the UEFA conference league competition already.
In terms of experience and achievements, there is no need to compare Mourinho with De Rossi, each era has its own people. De Rossi in his first season showed a good performance in domestic competitions, but in the Europa League his steps were unlucky, because he had to face a team that was never defeated, namely Leverkusen. It takes magic to turn things around in the second leg, it seems Roma steps just capable reach the semifinal stage this season.
The very realistic opportunity to be pursued is to finish in the Champions League zone or finish in the Europa League zone, the next three remaining matches must be utilized properly. De Rossi has reportedly received a permanent contract extension, management considers that he can meet next season expectations, but before that there is still unfinished business this season.