First, a little proper semantics-
what you want is not a "roll former"- that is a large and complicated
machine for making flat sheet into profiles linearly, like a gutter
And it is not a "slip roll"- that is a tool for bending flat sheet
metal into cylinders.
There are several types of machines that do what you want- there are
pipe and tubing benders which use a fixed die to make a repeatable
radius, and then there are three roll benders like you describe, which
are usually commercially called "angle rolls" or "section rolls", as
they were often used to roll angle iron into curves.
Commercially made motorised ones are, indeed 3 grand and up. And worth
it, as they actually work. I have a big one, and I love it.
Eagle imports some nice ones from Italy.
There are some hand powered ones available, but they are mostly for
flat bar the easy way, as there is a lot more friction involved with
bending tube or pipe. And you will need a dedicated set of dies for
each size of pipe you bend. Decent dies machined and heat treated from
good tool steel can easily cost 3 or 4 hundred bucks each.
These guys make rolls sort of l like what you want;
the one shot benders, which the auto and motorcycle guys use, are
another way of doing this- best is probably the hossfeld clone made
This is a job where the simple, hand powered tool really isnt the best
thing for the job- there is a reason why people buy the big powered
ring rollers, and its not just because they like throwing money away.
But for occasional use, one like the rdhs model might work. I would
send them a sample of your material, and have them roll it for you,
before I bought one. That way you can see if it squishes the inside of
the curve, or leaves marks- (some machines use serrated rolls to grip
the material, so it doesnt slip).