have you priced workman's comp for roofer's lately?
And liability insurance?

Oh and BTW, if you are paying a laborer on the side and they get hurt on your property, guess who owes? And home insurance doesn't pay, specifically excludes uninsured workers.

Plus you're going to pay extra because you did half of it yourself. Nothing worse as a tradesmen coming in to finish a half done job by anyone, much less a DIY job. (no matter what the quality of the job)