The match against Inter Milan at home will be the biggest test for De Rossi because the rivalry between the two is quite prestigious and As Roma must win if they want to catch up in the standings. It feels a little difficult because Inter Milan are in good form at the moment and De Rossi will definitely have a hard time facing them.
It was a very large test and almost impossible to complete. How could you give the match against Inter as a test for De Rossi? I mean, even if Roma loses the match, it doesn't mean that De Rossi is unable to carry out his duties well because the opponent is Inter Milan, the strongest team in Serie A at the moment. Maybe we can use the match against Ac Milan or Atalanta as a test for De Rossi to show the development of the team he is coaching. Or at least the match against Feyenoord in the European league. I think it would be more appropriate to look at De Rossi's capacity as the new coach of As Roma.
A difficult match can indeed be said to be a tough test. But as you said, even if AS Roma lose this match then it is normal. De Rossi hasn't been AS Roma's coach for long and he also hasn't been able to fully understand Mourinho's usual scheme for AS Roma. But so far De Rossi is doing a good job. And although the match against Inter Milan will be very difficult. But I might think that AS Roma can make a surprise against Inter Milan.
And AS Roma already have at least 3 wins with De Rossi. That is against Verona, AL-Shabab and Salernitana. And the next match could also be another test that might be quite easy against Cagliari. After that it was a tough test against Inter Milan.