Not a midfielder. Just doesn't have the dynamism or the guile. He's not quick enough in the head. You see Mata and Herrera using the ball with split second decisions, and it makes Rooney's overall play look like a slow-motion replay.
I still think he's a solid centre forward, but that is all he is. I just don't know what all these pundits are seeing when they say that they see Rooney being a midfielder in the next few years. If anything, I see it going the other way, and I predict he'll be more of an Inzaghi centre forward into his 30s, limited involvement and just playing on the shoulder. I think he'll always be a good finisher, but his mobility and quickness of thought will wane, and I don't think he's too strong at the latter anyway.