Depending on how much of the mast is above the roof line will determine if it is safe to do. If the fascia board is very sturdy, it should be OK, up to 8-10 feet without guy wires. Also, consider the size and weight of the antenna, rotor and so on. Now, the DISCLAIMER: You can do this at your own will, and take a chance it will not work. Make sure ALL of the structure you are using is in good sound shape. DO NOT use this application if it is near ANY power lines. It is best to guy the mast where possible. Use a good clamp, and lag screws to attach the assembly. I have done this, and have not had trouble. I have also built houses, and garages, and know the strength of various building materials. The main thing here, is YOUR SAFETY!!!!