I really don't understand why Daniele De Rossi has to be Mourinho's replacement. Because as far as I know, Daniele De Rossi also didn't produce good results in his first career as a coach at SPAL, a club in Serie C group B. But yes, young coaches can sometimes make surprises. For example, Arteta surprised us all in the Premier League.
Maybe being AS Roma coach is a great honor for Daniele De Rossi. This will be his first experience as a coach at a big club. And Daniele De Rossi actually has long experience as a player at AS Roma for 18 years. But I still doubt whether it will be a good thing for Roma or the opposite.
De Rossi always wanted to return home, perhaps there are some hopes that he will be able to work better at Roma, although a coach without experience is unlikely to be able to show something better than Mourinho.
I think that his stay at Roma as head coach will be temporary, because I don’t see any reason why he can improve his game. De Rossi will definitely not receive funding to buy new players and he will definitely need some time to adapt to the team. On the other hand, Roma has always been an ambitious club, and 9th place in the standings is too weak a result.