Make sure all contractors have their own insurance. Get a certificate and call the insurance agent to make sure.
Better make darned sure that the roofers you use, have liability and workers compensation insurance. Before they start, ask them for a certificate of insurance, naming you certificate holder.
You can get some sort of idea for business insurance at
http://www.best-american-insurers-free-c…
or home insurance:
http://www.servicesarticles.com/home_ins…
yeah, make absolute sure you're have extra coverage for all involved or that they have ample coverage. maybeit's best to talk to an expert
http://www.freeinsurancequotesonline.org
Get the work done from a roofing contractor who is reliable and has commercial general liability coverage.