I think he is a better CM than Rooney if you have to compare the two. I think they're different type of players though, Wilshere is more direct and more comfortable linking the defence to attack. Rooney is better at the joining the front two, which is what I presume Roy was hoping for (but...
Why does he have to be better? Slovakia are a different team, Wilshere plays differently to Rooney. Faster, more direct.
There'll be more teams to play as we're all but through already (even if in 3rd place). We've a 23 man squad, might as well use it.