Ferguson: Rooney back to old self after scoring
Rooney, who had not found the net since the Champions League quarter-final first leg against Bayern Munich, converted a first-half penalty after Ryan Giggs was brought down by Jonathan Spector.
Nani doubled United's lead five minutes into the second half with a superb finish from Rooney's clever lay-off and Dimitar Berbatov completed an easy victory with a rasping volley to leave West Ham without any points and bottom of the table.
United have seven points from three matches, level with Arsenal and two behind leaders Chelsea, but more importantly Rooney appears to be rediscovering his spark after an injury-plagued end to last season and a subdued World Cup.
"It was good Wayne got the goal but his performance was the important thing for me," Ferguson told the club's website.
"He enjoyed his football and was full of energy. That's good because he's not had a lot of football and he had a virus last week. But he trained all week and looked more like himself."
Rooney was watched by England coach Fabio Capello who will name his squad on Sunday for the forthcoming Euro 2012 qualifiers against Bulgaria and Switzerland.