The rollers are 3 3/8 "x 5" round bar, I drilled 1/2" holes through them with my tabletop drill press ( Biggest drill I had )the rest is just scrap, and an old engine stand.
It worked perfectly, until I tried to roll some 1/4" x 5" flat, It rolled it just fine, but it bent the top shaft, So I cut another roller, This time, I had to drill the roller with a hand drill, So you can guess how that worked out, The hole is not quite straight. It still rolls ok, but I had to add the side guides to keep my rings straight.
I want to try to make another one, I came across some SKF 1 1/2" pillow blocks, but I have no way to drill an 1 1/2" hole through the 3 3/8 " round bar stock.
So it will have to do for now.