You should also be aware that most spray painting contracts now call for "back rolling" if the spraying involved is spraying primer onto bare drywall or plaster.
The reason why is that the surface of drywall and joint compound are both porous. If you prime with a roller (or brush), then the force of the applicator actually squeezes the primer into the surface porosity of the gypsum and paper, and that results in good adhesion of the primer to the drywall when it dries.
The problem with spraying is that it doesn't force the primer right into that surface porosity; and that's what's suspected of causing adhesion problems with spraying primer onto bare drywall.
Another thing to consider is touch ups to the walls from repairing nail holes and such. Sprayed walls are much smoother than the "nubbly" texture that a roller leaves behind on the wall. If you repair a nail hole or fix a wall, then you want that repair to be invisible, and that requires more than the paint being the right colour and gloss. It has to reflect light the same way as the surrounding wall, and you can't match the smooth surface of sprayed paint with a roller.
So, if it wuz my money, I'd just apply both the primer and paint with a roller to both insure good adhesion and avoid any problems with repairs showing.
Last edited by Nestor_Kelebay; 01-30-2010 at 09:46 PM.