An employee was feeding an assembled truss into a finish roller to press truss plates into place. The truss was not centered in the opening so it contacted the left vertical safety stop and the rollers stopped. He tried to reverse the roller, but it would not turn back on due to the safety stop being engaged and wedged against the truss tail. He attempted to pull the safety stop back into operating position. When he bent it around the truss, the rollers started moving and the tail of the truss went up the vertical safety stop and pushed his finger against the truss tail. His left pinky fingertip was pulled off the bone.