Rosler, the former striker who played for City during the 1990s, will never forget how Blues fans supported him during the battle against cancer he went through after being diagnosed in 2003.
The 45-year-old German has no doubt that hearing thousands of City supporters signing his name over the phone while he was in hospital was a key moment in his route to recovery.
And asked if Sunday's contest would be an emotional affair for him, Rosler said: "I would be lying if I said no.
"But I have to make sure that the professional side takes over and not the emotional side.
"That will be my personal focus on the day - to look to enjoy the occasion, but to make sure I'm absolutely concentrated on the job in hand."
Asked if it would be difficult to divorce himself on the day from the bond he has with City, Rosler said: "It will be interesting.
"When I was just recovering from cancer and had finished with my treatment, I went there to say thank you for the support I got from the club and from the supporters, and that was a very emotional moment.
"Now, all these years later, I'm going to be there with a wonderful football club as a manager.
"It is quite a story, and the emotions will be there, but I also know I am a very professional guy and I can focus on the job in hand.
"So we will see - ask me after the game!
"It was very special, the way they helped me to recover. It was a very important moment, I always felt.
"It put a smile back on my face and gave me new hope and new motivation to get through a very difficult time."
The encounter at the Etihad Stadium is a rematch of last year's FA Cup final, which Wigan famously emerged from with a shock 1-0 win.
The goalscorer that day at Wembley was midfielder Ben Watson, who this week agreed terms on a new contract with the Latics - the following month after suffering a double leg fracture.
Rosler, appointed as Wigan manager in December, said: "I'm not sure he has signed, but it has been agreed.
"I think it is fantastic from the chairman (Dave Whelan) and our football club - to support Ben in such a difficult time.
"He is a special player, and this is why we already started contract negotiations in January. Ben was very willing to continue working with me, and obviously then this has happened.
"I think it is a fantastic gesture from our owner and our football club.
"I'm sure he will repay us. He has come back once (after breaking his leg in 2012) and he will show everybody that he can do it the second time as well."
Asked how Watson, who sustained the injury in a Sky Bet Championship clash with Barnsley on February 18, was progressing in his recovery, Rosler said: "At the moment it is more a mental thing I think.
"The first few days were very difficult for him - for all of us, but especially for him and his family. But I think at the moment he is in very good spirits."