The Strasbourg coach is on track to be named Enzo Maresca's successor at Chelsea - potentially as early as today.
Rosenior acted as Rooney's assistant manager at Derby County and the Manchester United legend said on his podcast: "He's taken chances, and hopefully that pays off because I think Liam is as good a coach as I've ever worked with.
"Liam was so important for me. He was incredible in his coaching ability. I was more of the manager and dealing with players and everything.
"So I learned a lot from him from that point of view and then I think he's done a great job as a whole."
Rooney also said: "If he goes in there, he won't disappoint. He's been waiting for an opportunity like this.
"If you don't take it now, then you're never going to take it. And I think he's done his apprenticeship, he's done his work to try and get to that job.
"So he'll have no doubts in his mind that he's capable of doing that job. And hopefully, very soon, hopefully we hear that he is the manager, because for young English coaches I think it's massive.
"We don't really see English managers at big clubs. So he'd be leading the way for for us."