The possibility is still there but actually I'm not quite sure whether Ronaldo will return to Serie A or not because there is indeed a past with Juventus which of course will have some intersections later.
But there is still a possibility because in this case Ronaldo's transfer is sometimes unpredictable, like when from Madrid to Juventus without much news and from Juventus to MU suddenly it is not impossible indeed if he goes to Rome in a fast time and without the media knowing.
Possibilities are always available for everyone but currently financially AS Roma is not in a position to bring a player like Ronaldo and settle him he is having a very high salary and it's one of the most important points as we already watch in Mbappe case there was rumor's he is going to leave PSG for Real Madrid but after having luxury contract now he is going to stay here for very long time.
Even Manchester United is not in a position to give any luxury like this Ronaldo but now it's in his sack to stay here and end his career on a high note at the one-off best club in the world because he is already 37 and can leave this game anytime so staying here and giving his best for good future of Manchester United is also good for him.