MAINTENANCE CREW HAD CHANGED BAG DELIVERY EQUIPMENT FROM AN ADJUSTABLE BELT CONVEYOR SYSTEM TO A FIXED ROLLER SYSTEM 3 HOURS EARLIER, WITH NO WAY TO STOP BAGS ON CONVEYOR FOR 2ND EE TO GRAB & THROW BAG ONTO PALLET. EE TRIED TO CATCH 50# BAG FALLING TO THE GROUND, STRAINING HIS RT. SHOULDER.