As a roofing contractor, we don't and won't itemize quotes other than material options. When we install a roof, we install a system, not just a material. All of the components have to function with each other, underlayments, ventilation, flashings, fasteners, starters and capping.
If I have a customer that wants to do their own tear off, I walk away. If I have a customers that wants to use 3 tab shingles on a dimensional shingle I walk away. If I get the feeling that a customer has unrealistic expectations of how the process works or the final outcome, I walk away. I can see both sides of the issue and when I go out and do a inspection of a roof, I'm also determining if I want to work with this customer. There's been more than one occasion that I wouldn't work for a customer if they paid me twice as much upfront to do their roof.
Key is, finding someone you are comfortable with, get several quotes and NEVER pay in full until you are 100% satisfied.