L.A.
Hi C.,
Years ago, I was a claims adjuster, so I understand your question. Also, I have been out of this industry for several years, so some things have changed. Thus, I am no expert, nor am I giving you any legal advice ;-)
Technically, asking them to waive the deductible is something that is "under the table" and they really don't owe that to you, unless they fill it means them getting the job or not, and they make a verbal agreement with you.
If, you have the check and it's made out to you and the roofer, then you're going to have to use that roofer and submit his final bill to get him paid for the difference, less your deductible.
If, you have the check just made out to you, you can choose another roofer and try to negotiate a better deal. But, ultimately, you'll have to submit the final bill to your insurance and they are only going to pay the difference of what they already paid, the final bill, and less your deductible.
The only way to get it done for less and pocket some money, is to do all the work yourself, and then the insurance should pay you the average amount of 2 or 3 other estimates.
Take care & God bless,
L.