The Sky Sports studio was a hive of activity on Sunday as Roy and Jamie debated whether or not to start the Portuguese player against the Blues.
The 36-year-old was named on the bench by Michael Carrick, instead starting with a front three of Jadon Sancho, Marcus Rashford and Bruno Fernandes.
After the final whistle, the man who came on for Sancho made little impact on the game, and immediately went down the tunnel.
Sky Sports pundits argued about the logic of signing him from Italy, with both saying that he should be an automatic starter.
The debate was in full.
What should the new manager do with the player?
Roy Keane said to play him.
"Start him?" asked Dave Jones.
"You have to," Roy said. He was probably freezing when he came off the bench. There is no chance that he will sit on the bench at Manchester United.
I don't know why Carrick is trying to giveRonaldo a high-five, he leaves the pitch immediately when the final whistle sounds. There is nothing wrong with a player being upset. There is no chance that he will sit on the bench at Manchester United. What is the point?
He is a great player. He has gotten some goals and assists since he came back to the club. This idea that he is going to start closing people down? He's not. You have to work with a celebrity. I've played with players who don't do the things you want them to do, but they score the winning goals in tight matches.
Ronaldo has to be in the starting lineup.
This idea of resting him? They are not playing again until Thursday night because they didn't take a lot out of the players. He could have played well today.
After 64 minutes,Ronaldo replaced Sancho.
Do you think Rangnick will see that?
"No." Jamie Carragher. I don't think it's right for a player to be put on the bench and start every game, but I do think that it's not a problem for the player to be put on the bench.
I can understand why Michael Carrick didn't start him in the big game.
In the first game of the group stage, when they were down to 10 men in Switzerland, Ole Gunnar Solskjaer brought him off and they lost the game because of a Jesse Lingard bad back pass.
There was a big story that he brought off. He's 36 years old. He didn't start him againstEverton and then he walked down the tunnel.
"Now, he's not the player he was." I don't think it's a big deal if he doesn't start every game or if he comes off in a game of football.
This is a big game for Manchester United. I understand that some of the group games are not going to be good for Man United, but if you see him in the car park, you see a player who has won everything in the game. He will want to play in these games.
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There were highlights from the draw between Manchester United and Chelsea.
"That's every player when we're playing the game."
"But they are not all world class!" Roy said. They won't have had 800 games in their career. If you were watching Man Utd today and they were poor, you would still think that if the ball falls to anyone in world football, it'sRonaldo. It's not like he has come back to the club and not scored and you think he's not up to speed. He's on it. He looks interested.
He gets the blame for the high press.
"He doesn't press, does he?" asked Jamie Carragher.
He's not being pressed for four, five, six years. I told him that he wasn't going to fix Manchester United's problems. You don't bring him back to Man Utd to sit on the bench.
He is not going to start every game. You might get one or two balls into the box, and you want to drop the player?
"Do you think he pressed today?" Roy asked.
Why did Manchester United sign a player in the summer? They signed him because they were afraid he would go to Man City. That's the reason they signed him.
There was no plan to sign him. He was going to go to Man City and they signed him at the last minute.
He was always going to play. They were going to sign him to not go to City but to sit with us on the bench.
I didn't say that. I'm wondering if a Manchester United manager is allowed to put a player on the bench. The guy that's played has scored the goal.
"Of course he is," Roy said. Show me his statistics because they have taken over the world. His statistics since returning to Manchester United are good.
Goal scoring is a thing, yes. Definitely.
"What's the game about?" Roy asked. Jamie, the game is about goals.
Where are Manchester United in the league? Is United close to winning the league? That's what he's been brought back for.
The game is about goals, Roy! What did Ian Rush do? He scored goals!
Did he press as well? The man doesn't.
He did, but he didn't score as many.
I'm not saying that he's a bad player. What can he do? He's a phenomenon in terms of goals, but I mentioned this to Lionel Messi.
Messi has been signed by PSG. Man Utd have signed a player. They are two of the best players of this generation. Two of the greatest players of all time.
Is United close to the league title than they were last season? No. Is the team closer to the league with Messi in it? No. Football is a team game, and we talk about goal scorers or whatever position you are, but football is a team game.
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Roy said he was never in the running for the manager's job at Old United.
Dave Jones: "So do you think signing him was a mistake?"
"Ronaldo was never going to get Man Utd back winning league titles," said Roy.
What was the point in signing him? He's 36 years old.
To win the trophy! It's about awards. Did you win the cup?
"Yes, I did," said Jamie Carragher.
Roy said that he had come back for the FA Cup and the European Championship. They have made it to the next round. How much do you think that is worth to the club when you look at the business side of it? That's what he wants.
If you finish second last year...
"Second is not good to you...", said Roy Keane.
"I know!" said Jamie Carragher. You signRonaldo at 36. You will not win the league in four years. Right now is when you should sign someone at 36 or 37. If you sign Raphael Varane, a four-time European champion and a World Cup winner, it's to win now.
Roy said that a few months ago whenRonaldo signed for Man Utd.
Are they any closer to the league right now?
There is a man on the bench at the bridge.
"No!" Roy Keane said. He did not return to win the league.
What's he going to do then? What is he here for?
Roy said to help them win a trophy.
"What's he here for?" asked Jamie Carragher.
"Mourinho won a few trophies but he didn't win the league," Roy said.
"Oh my..."
When you won a trophy, were you not excited? Man Utd are in a cup competition.
You said that the league never had a winner. What is he here for? What are you doing at Man Utd?
"Cups!" said Roy Keane. "Cups!"
Is that where Man Utd have gone? We're happy with cups.
"Yes!" Roy Keane said. That's where they are a club. Look at the team! Look at the last two or three years of the league. I can tell you that they are not going to win the league for the next two or three years.
If United don't win the league in the next two or three years, why did they sign him? If they are not going to win the league right now, start getting Jadon Sancho on the pitch.
They were never going to win the league. The gap was never going to be close.
There's no point in signing him.
"I'll say it again, to win some trophies," Roy said. That's where they are.
What's next?
The game between Man Utd and Arsenal is on Thursday. The Sky Sports website, App and YouTube channel will have free highlights from the game.
