A Ronaldo I know he always keeps his word, yes he is responsible for paying for what he said when he joined Manchester United. Even though he couldn't make it happen at least he helped the club for it. But judging by now Ronaldo will still stay at Manchester United. I think it proves that he will still be in the city of Manchester.
Manchester United poor performance this season is the reason for the rumors of Ronaldo move to Roma, but I personally think it's just a rumor that doesn't have a strong reason to consider it valid, so far Ronaldo has a love for Manchester as a team that has raised his name and last season he back to manchester determined to return to make the glory of Manchester United, so there is no reason for Ronaldo to leave manchester united so soon, now manchester united has had a new coach and is now starting to look for some players to improve their squad next season as ronaldo wanted all this time.
I guess you mean their poor performance last season because the league has not started yet. About the rumor of Ronaldo's possible move to AS Roma didn't come as a surprise to me because Manchester United didn't qualify for the Champions League next season and as a matter of fact, Ronaldo will want to move to a team where he would possibly be seen in the champions league.
It is still considered a rumor because Ronaldo personally said he is happy being at the club despite their poor outing last season and he said he is hoping to help the team to get back to its normal shape so personally I doubt if he would go against his words by signing for Roma.