An Adjustable Lift Bar System for roll off containers and other applications used to enable a roll off to be compatible with a lift bar hoist system set at various heights; the system includes a lift bar having a crown; a pair of lift bar flanges and mounting flanges with a set of holes to receive removable fasteners and mounting flanges; a long spreader tube between the mounting flanges; a pair of short spreader tubes, bolt plates with a series of holes, the pair of vertical supports, and fasteners to adjustably secure the pair of the mounting flanges of the lift bar assembly to the pair of the bolt plates.