I have a Corona mill that I run with a power drill, and I imagine my results that are similar to what you would get with that.
As it is my brewhouse efficiency varies between low 70s and mid 80s.
I figure that if I had a roller mill I could get more consistent results that stay in the 80s.
As long as you're going to spend money, I would recommend springing for a roller mill.
Search this site. There have been several discussions on the merits of different mills.
There's all kinds of them out there. Shop around.