I had a roof done 3 years ago. I got 3 prices and went with the low one. Local guy, lots of references, and a GAF master rated installer for a 50 year roof.
I wrote a spec sheet for workmanship, cleanup etc. I also got copies of their insurance certificates naming me as additional insured, and copies of their workman's comp certs. You cannot work on my house as a contractor without insurance
Insurance is a major consideration. Contractor liability is important, but workers compensation coverage is absolutely vital. For the roofing trade workers comp is also very expensive.
The primary reason why most roofing crews are subcontractors is that subcontractors are not employees, thus generally outside the requirements for workers comp, unemployment insurance, social security/medicare (state laws will vary on this). Your roofing contractor is not providing workers comp for the sub crew; the subcontractor is responsible for his own.
Generally speaking, when an unlicensed contractor is working on your property that person may be considered as a temporary employee UNLESS YOU HAVE A WRITTEN WAIVER (and your state law allows such waivers). In the event of an injury YOU MAY FIND YOURSELF RESPONSIBLE for all hospital, doctors, rehabilitation, wage losses, potential disability expenses AND YOUR STATE MAY HAVE LEGAL AUTHORITY TO PLACE A LIEN ON YOUR PROPERTY TO COLLECT.
Your homeowners insurance policy conveys no such insurance coverage (unless you have added specific additional coverage at additional premium costs), and even then such coverage is likely to exempt such contract workers.
But, but, but my state law requires licensing! (People lie).
But, but, but my state law requires insurance! (People lie, and insurance certificates can be forged pretty easily).
But, but, but that's just not fair! (Neither is life in modern America, so hand over your keys and deed).