Depending on the size of stock you are rolling, its going to be difficult to mind numbing. Of all the tools I have made, the ring roller is the most curse inducing. My advice, get a boss bender if you need heavy stock bends. Make sure its got the acme thread adjustment. A small bender can be made for thin stuff but you can go to harbor freight and buy one that will handle 1 inch by 3/16 for about 50 bucks. The biggest boss bender will handle 2 by 1/2 if memory servers. It runs a little over 600. Its the gearing that gets you on these things. My vote, spare yourself the agony, buy one.
Trenton Tye
Purgatory Ironworks

There is a ring roller on EBAY(buy it now) from Proline that runs around $165. It's a hand crank, but it can be converted to electric with a little manipulation.

Jake

Start With D.O.M. (drawn over madrell) tubing. 2.5 inch O.D.x1.25 I.D. Or thereabouts. Cut to length (3"-6"). Put a large chamfer on the inside of each end. (round file, die grinder, or a broken off bit of round file in a drill motor. Chamfer the ends of some 1.25 dia. cold finished steel shaft. Heat one end of tube red, press shaft in a little. If You do not have a press, Hammer it. Here is where a large bevel on the end will prevent damage to the shaft. Weld tube to shaft (fill tube chamfer). One roller needs bearing lenth shafts at each end. One needs room for just a bearing at one end and a bearing and a sprocket at the other end. The third needs bearing, sprocket at one end, Bearing, sprocket,and hub at other end. Gear redution is simple. Make large ring like old steel wagon wheel. 5'-6'dia. Use same size D.O.M. tube for hub of wheel. Bump bend with hammer and vice if you have to. 5' wheel w/2.5" roller gives 24-1 ratio. Use small diameter chain sprockets on other end of the two non-ajustable rollers, Connect with chain(40 picth or what you have) If you can't cut keyways, grind flat spots on shaft. On drive hub, use .5" dia. set screw on flat spot of shaft. Look up pictures of a blacksmiths tire bender for inspiration.

Bill Stark
Check Machinist's Workshop magazine (Village Press) Dec 07-Jan 08 issue Vol. 20 No. 6 for an article giving complete instructions with good photos. I have not built it yet,but plan to soon. This one calls for a lathe, but if you're an improviser you should be able to adapt his approach to the resources you have available.

I have my grandfather's tire bender, which he used in his blacksmith's shop. I'll try to take some digital photos and upload them when I figure out how.

don't know if my previous comment was posted so sorry if its a repost.
My homemade ring roller is not Mind numbing as per a previous comment made to your question. Made all my dies without a lathe. They are 3inch round CRS and were entirely done on the mill. Very simple and easy to do and I'm not a machinest, just a hobbiest:) Made them for .875, .5, 1 inch tube. You get very nice bends and I use them for making large radi. I was using conduit benders before, but this new tool has improved the quality by 10 fold.

got the harbor freight roller for $65

just a little mad at myself for not buying one sooner.

for the last few years i've been turning 1/4" round stock by hand using pipes

Ring roller: Don't know how "live" this one is, but I'll attach picture of very simple ring roller I made that'll do up to about 3/8" X 2" for gentlish curveson gate tops et.c. The polyurethane drive wheel grips the material nicely preventing slippage. Still use it despite having acquired and motorised an old tyre bender. Incidentally, anyone wanting to add a chain drive to rollers et.c. I'd recommend cannibalizing an electric hoist. For not much money you get a nice slow torquey motor with a remote forward/reverse switch included. I've done this with both my tyre bender and sheet metal rolls. Only thing to watch out for is that somewhat to my surprise the little hoist I used for my sheet rolls doesn't have the same power in reverse as it does forwards! (Guess it only needs to act as a brake when used as intended)