Ronaldo missed most of United’s pre-season preparations after submitting a transfer request last month.
The 37-year-old, who currently has one year left on his contract at Old Trafford, made his debut under Eric 10 Hager in last week’s draw with Vallecano.
Ronaldo’s former Manchester United team-mate Rooney believes now is the right time for the Red Devils to part ways with the five-time Ballon d’Or winner.
“I think Manchester United should let Cristiano Ronaldo go,” Rooney wrote in his column era.
“It’s not that Ronaldo can’t play in ten teams. He can play in any team. Ronnie will always score for you. But my personal opinion is that Manchester United are not ready to challenge for the title right now, So the goal has to be to build a team that can win the league in the next three to four years, and you have to plan for that.
“If reports of Cristiano wanting to leave the club are true then United should allow him to go and get a No. 9 for the next three or four years and really help them build a team that can be a success. A witch must have time to do it.”
“Cristiano Ronaldo has done more in football than anyone could have hoped and imagined,” Neville said Overlap of sky stakes.
“He’s going to be one of the best players of all time and always will be. What happened at Manchester United this summer will be forgotten in 20 years.
“But as a former Manchester United captain, I think it’s unpleasant to me that the star players in the dressing room are playing at this time.
“This has happened from time to time in the past few years, you have been in [Paul] Pogba’s agent – not necessarily Pogba – but his agent is always in play.
“You can’t have your star player run the store at the club. You can’t have it. So when Sir Alex Ferguson used to let a player go, it was because that player needed to be moved.
“I know Manchester United fans want Ronaldo to stay. But if Ronaldo wants to leave, Manchester United – in my opinion – should facilitate that.”
It is unclear whether Ronaldo will play for Manchester United in their first Premier League game of the new season against Brighton on Sunday.
But manager Ten Haag said he was happy Ronaldo was still part of his team.
“How do I feel to start the season with Ronaldo? I’m really happy,” Ten Haag said.
“I told you before: we planned this season with him. We have a top striker and I’m really happy he’s here, he’s in the team and we stick to the plan.”