When I was teaching at Pratt Institute one fellow had his class making 4' x 6' prints from paper rolls in the same darkroom where we made 16" x 20" prints as the largest. He gave me a tour of his set up. They had constructed what are best described as troughs made form clear acrylic sheets (Plexiglass). The troughs were, maybe, 54" by 18" by 18" if I remember correctly. The paper was tacked to the wall and a Beseler enlarger was set up to do horizontal projection. The paper was then rolled into a tube and put in the trough, where it was rolled and unrolled during development and so forth. I personally never used that set up, and didn't see it in action, but the prints were fine.