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.
Worrying about troubles with Ronaldo and his attitude is one of biggest barriers for any club want to sign with Ronaldo. They see more risk, more troubles with Ronaldo than what they can receive from him.
Ronaldo must change his attitude and accept to have a flexible role in any club. Sometimes if he plays well, he will be in the squad and get important position but if he plays bad, he must accept a position on bench. This will make him a more useful player than a troubling one.
The sentiment in Napoli is very positive and good, hence they don't want to have a troubling player like Ronaldo. They must completely focus to win their first Scudetto after many decades. Any unnecessary trouble is not wanted by Napoli and Spaletti. It is their most priority, not about salary or transfer cost for any player.
Almost all English league clubs refuse Ronaldo to be brought in maybe because they know how Ronaldo's attitude will be an obstacle later so that many are ostracized and not on the radar of English club supervision this winter.
Of course attitude is important especially Ronaldo should be able to set an example to others that attitude in football is not like that if they don't play well and have to accept the reality if they are substituted, but Napoli are really interested in Ronaldo even though we know the Napoli squad is on fire but maybe Spalletti wants to need Ronaldo's services as long as he changes his bad attitude for the better.
If it is true that Ronaldo goes to Napoli, he must be willing to cut his salary significantly because the highest salary at Napoli is 90 pounds while Ronaldo is currently at Man United receiving a salary of 360 pounds, so it will be a drastic drop and not have an impact on his game.