I'd put my money on the roller idea too! New homes are usually sprayed because it is less time consuming and therefore in some instances (multiple houses being painted) more cost effective to the builder.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.