Two employees were working on a roof above 20 feet, both tied off. Work was also being done about 60 feet above them, and debris from that work was striking the employees. The employees detached their lanyards and got closer to the edge of the roof to get the attention of the employees who were blowing the debris down onto them. One of the employees fell from the roof to the concrete about 14 feet below, breaking ribs and his arm.