Heavy duty pipe/ring roller

[Frank S]

I might offer a little input if you would like. From the pictures you provided your drive rollers are not as much being too far apart as they are way too small in diameter
The optimum major diameter of the drive and idler roller dies would be 4x the diameter of the pipe being rolled this would afford a better drive friction to pull or push the pipe. The depth of the radius grove would be half the OD of the pipe with the radius of the grove matching the radius of the pipe being formed. The ram for adjusting the bend radius should be on center-line with the idler die for maximum strength and reduction of the creation of a bending moment in the mounting structure the idler is mounted in.
I am not at all confident the shaft in the gear reduction housings will be able to take the side loading stresses but I have no data on its size or specs it may be fine as long as you do not apply too much power to the ram on each pass. Good luck