"Giuseppe is a great talent and an exceptional finisher, one of the best I have ever seen," said the popular Norwegian.
"He has a football brain and he thinks about scoring goals before he gets the ball.
"His movement is good; he is quick and strong; his work-rate is tremendous, and mentally he is class. He is also humble enough to know he still needs more experience.
"But there is no doubt he is a very interesting prospect and has a very bright future indeed."
Rooney is also impressed by him
"Giuseppe is a great player and one to watch out for,"
"I see him every day in training and he really impresses me.
"His touch, feel and awareness are brilliant. He is perhaps the best finisher at the club and he will only get better."
The lad himself talks about the joys of playing at Old Trafford..
"Providing an `assist' is as good as scoring a goal," said Rossi.
"I always look to get on the ball and try to make something happen when I get it.
"Every young player wants to play in front of a big crowd at Old Trafford, and I just want to impress the management enough to keep these kinds of experiences going.
"There are so many great players here, but I feel I am learning a lot just by training with them. I hope that will help me."