Employee was loading B.O. belt rollers into the bucket of a scoop (LST-5S). He picked up a bottom roller & slipped on some wet rock dust which caused a sudden movement & strained his lower back. He stayed on the job until the end of his shift & then was taken to the E.R. at Castleview Hospital. He was diagnosed with a muscle sprain/strain and taken off of work for 3 days.