An employee was operating a telehandler to set trusses on a new construction site. The employee was making a y-turn maneuver to position the telehandler perpendicular to the sidewall and raise the small post frame truss up and over the 12-foot sidewall. The telehandler was on a steep grade. As the employee was making the maneuver, the telehandler began tipping to the side. The employee attempted to jump from the operator's seat and was struck by the roll cage. The employee was hospitalized with lacerations to the forehead and fingers.