I built a set of rollers to determine how much I enjoyed riding them. They were made from 3 inch ABS pipe, which I finished with drilled end caps, fitted with lag bolts. The bolts fit into ball bearings(scavenged from a skateboard) which were recessed into the 2x4 frame.
This build was intended as a proof-of-concept but worked sufficiently well that a second version was not required. The only deficiency I encountered was from poorly triangulating the cap centers(I used a tape measure and hand drilled the holes) which resulted in vibration at high speeds.