Grain mill bearings/bushings

I have been stalking every possible thread about DIY grain mills. I am not mechanically inclined. My buddy is going to knurl some rollers for me, for the price of helping him brew his own beer. Now once those bad boys are ready to be mounted... how do I keep them free rolling?
I have seen bearings and bushings, but none too clearly. I am an idiot and thigns need to be in my face for this to make sense to me.
Bearings seem easy enuogh, but I have to make sure they fit snugly in both the rollers and the housing, correct? How is that possible? I just picture the entire bearing slipping around in the housing.
Bushings seem really easy, but wont they wear the roller's shafts after awhile? Do they get lubed?

Please help this ntiwit. :cross:

Thanks!

Most mills, I have seen, use an oil impregnated copper bushing as the bearing..