Employee stated that on 1/15/09 he picked up a bottom belt roller & carried it approx. 20' & threw it against the rib. At this time he felt a ""pop"" in his left shoulder. This incedent was under investigation & upon the diagnosis from an MRI on 1/27/09 it was determined that this employee has a torn rotator cuff & is being reported at this time as a result of the diagnosis