Ferguson believes his derby performance will see Rooney rediscover the deadly form that saw him score 35 goals in all competitions last season.
"Wayne has weighed in with his two goals and it's great to see because knowing him, he will go on a run now," said the United manager.
"That's the kind of player he's always been.
"His finishes were terrific. They were good cut backs from Ashley Young and Rafael. The first goal was down to Ashley Young's determination to get beyond defenders and play him in - and he knocked it into the corner of the net.
"They were two good finishes. He's made a really good contribution."