Geez Robbie, good question. You'r in deep sh*** there. How high are you over the roof top? Can you avoid crashing on the rooftop by using Vuichard by going sideways? Rather crash on the roof top and not falling of it?
Do you have power left or is the RPM already decaying? Why are you downwind anyway? Obstacles? Probably you shouldn't have tried that approach in the first place. That would be the right solution. Planning and avoiding.
No really, can't say I would know.