Everyone has the same expectation about AS Roma, but maybe the decline that occurs requires time to return to its best performance, a lot of blunders at the beginning of the season and strategies in the game are very far from the effectiveness of last season's strategy.
Several key AS Roma players suffered injuries at the start of the season, I think this was one of the factors in the decline in the performance of Mourinho squad. I agree with your opinion that ups and downs in performance are normal, especially since Roma is not active enough in the transfer market in hunting for players. Lukaku's presence can at least help the Giallorossi improve their performance, if they can finish in the UCL zone I think that's good enough.
I think inadequate financial factors mean that Roma cannot have much say in Serie A, in contrast to Inter, Juventus, Milan, which last summer were quite active in hunting for players. So the results that Roma are currently achieving are very commensurate with their expenditure, I think if Pep Guardiola were in Mourinho current position the situation would not be much different.
Jose Mourinho is a very good coach, a proven one for that matter and with the right backing and financial support from the board he'll recruit good players that would elevate the performance of the team and make them one of the the strongest side contending for the league title, but since the club is not very financially capable of backing him up he'll have to manage the ones he's got, although Lukaku is a very fine addition to the team and I believe he'll do his best to help them achieve success this season, probably securing Europa or conference league spot.
It's not easy to tell if Roma would finish I'm the UCL this season giving that their performance so far is not compared to that of Inter, Napoli, Milan and Juventus, but it would be so surprising to see them finish top four, because Roma didn't really invest much in recruiting new players like other big clubs did however I'm impressed with their performance in the Champions league match against Sheriff Tiraspol.
.