The striker has only scored from open play in one game this term, when bagging a brace in the 4-2 win against Stoke City in October. Rooney also converted a penalty in Braga but missed from the spot during the 2-1 win over Arsenal.
The boss believes it is only a matter of time before the England international is firing on all cylinders again in front of goal after he went close against West Ham when forcing Jussi Jaaskelainen to make a smart save.
"Wayne is going through a period like all strikers do," said Sir Alex. "He is not scoring. It will change once he starts to score reasonably regularly. Then it will become better for him. Also, he has missed bits of games. He has been off with tonsillitis. Wayne is the type of player who can't miss games. He needs to play all the time. I am happy with that part of his game [assisting goals], that is fine. If he can contribute to the team's success, then fine. But we would obviously like him to score more."
Any partnership with Robin van Persie is still a work in progress but the manager thinks the team are starting to learn how to bring the best out of the summer acquisition from Arsenal.
"With Robin coming, without doubt he is an up-front player," explained Sir Alex. "There is no question about that. He has experience and now our players are starting to realise how good he is. Hopefully that understanding gets better. There were some games where the way we kept possession was middle to wide, to middle to wide, without using the frontal area. We are getting more aware of the runs he's making and his movement up front."