The former Netherlands boss has introduced a new 3-5-2 formation to the Red Devils this summer and it paid off with a 3-1 victory over Liverpool to claim the International Champions Cup on Monday.
Rooney scored his fifth goal in three pre-season games by netting against Brendan Rodgers's side and the England international says that the whole team are thriving on the Dutchman's no-nonsense style of management.
"It's been a good few weeks. We've got a new manager who wants us to play a different style of football," he told the media.
"We've had to adapt. We've had some good results against top opposition so we can be pleased.
"I think the system suits the team, not only myself. The manager came in and had a look at the players we've got. He's done what he thinks is best suited for our team.
"He's a tough manager but he's been great since he came in. He's given us all a different way of looking at football, which we haven't had before. It's been great for us and hopefully that will continue.
"We wanted to win games, play well ad obviously we've done that. We've won a trophy as well. It's always nice to beat Liverpool. We're happy with the work we've done out here [in the United States]; now we go on to Valencia and then the season starts."