Falls often occur on roofs because of trip hazards. Whether it is a loose shingle that has not been nailed down, a hammer someone set down, or the bag the shingles came in blowing around the roof. The hazards are everywhere, and we haven't even mentioned your fall protection.
When you add your fall protection to this obstacle course, you are creating another tripping hazard. As you know you often have 50' of rope, but you are only using 20' of it. So the rest of your lifeline is going to be laying in front of you. Add an air hose you've added yet another way to send yourself flying off the roof.
Why not try the MAX X-LINE developed by Super Anchor?
This is a safety line made to cut down rooftop obstacles - it's got a rope and pneumatic airline rolled into one. The tough lifeline material is wrapped around the hose which will remove one more trip hazard on your roof.