Roma's game is still quite good. there are good players like Dybala and Lukaku in the team. Mourinho's departure didn't have too big of an impact on Roma's game. but you can be sure that Brighton will make things difficult for Roma in the next match. but if Roma can get up now, maybe Roma will become a competitor to Liverpool and Leverkusen.
However, in the group stage, we saw a bad game from Roma. and now they are rising again to try to enter the European League trophy competition.
Not only Mourinhos departure didn't do any damage, but they actually became better after he left as well. Which really isn't great for Mourinhos legacy as well, dude has been around for a long time and he still ended up being wrong in most cases, I feel like it wasn't really all that easy to handle.
I personally believe that the best thing to do in this case would be Mourinho to go to Saudi Arabia, because they would hire him just based on his name alone. De Rossi on the other hand may have a much better career after this, because he took over a team that weren't doing that well, and ended up having some great wins, and even streaks, to keep the team alive and doing well. These all matter to him, and should be important.
AS Roma did seem to find a new rhythm post-Mourinho, which makes me wonder how his departure affected them. According to my observations, Mourinho led Roma to the UEFA Conference League title and Europa League final. These accomplishments show that Mourinho can still lead teams to European prominence despite recent losses. But I believe that his methods and management style may not work for every club at every time.
You're partly right about Mourinho going to Saudi Arabia. He may start over with his name and experience valued. I dont see a manager of his calibre leaving European football just yet. De Rossi has revitalised Roma, especially in Serie A, impressively. His turnaround skills demonstrate his management capability. Like you, Im cautiously excited about their Europa League chances.