Rooney has now scored nine goals this season, five of them for England.
“I am really pleased with my form and hopefully I can keep this good run of goals going,” Rooney told BBC Sport.
“I have worked on every part of my game in training; it’s starting to pay off.”
“Wayne is only 22,” added manager Sir Alex Ferguson.
“We expect him to improve, as we did with Ronaldo. But he is a member of the team, just like everyone else.”