What to expect from Ronaldo by Spalletti? I don't think Ronaldo will make much of an impact, maybe it will only add to Spalletti a new problem. His nature at Man United should know what will happen if he brings in Ronaldo.
I think it will be more trouble than profit. If Ronaldo's price is still expensive, of course it will not be worth the gain. I think Napoli are better looking for a talented young forward. It's not buying an old player who is starting to lose his best strength.
Ronaldo can bring more confidence for Napoli players. Also, italian league a bit have a slow playing rythm, so if Ronaldo join to Napoli, he can give a chance to bring trophy since with his skill and his performance, still applicable for Serie-A. Don't forget about money, merchandise sale can help their finance. The only problem is his salary, i'm sure maybe hard for naples to pay him.
If Cristiano Ronaldo is given the opportunity, I'm pretty sure he can have a positive effect on the team he plays for. Especially if the game scheme goes the way he wants it to. I saw at Manchester United, he didn't receive a good ball supply from his team-mates and also his team-mates didn't understand what kind of ball he wanted. The problem we see is him with his coach which I see is getting worse every day.