Pull out your mortgage note.
It actually says "mortgage note" at the top of the paperwork. Read it, my guess is that it states that the home must be kept in "livable condition" and likely has other contractual obligations that you the mortgagee are required to abide by. In the event that the Mortgagor determines that you have not abided by the terms in the MORTGAGE NOTE then the Mortgagor has the ability to do what is called "calling the note due" this means that it is required to be paid in full immediately.
So... Read the note. Determine what is required of you. (Im sure it's something)
Then do it, or pay off your mortgage.
Insurance Fraud
it is only FRAUD if the damage did not occur. If the damage did occur and occurred as reported, etc. then the homeowner did not commit fraud.
IE we took a power surge in 2010, I lost the following items in the surge;
2 TVs, 3 computers, 1 microwave.
I got a check to replace the above (as I was properly insured, know that electronics are not covered in the event of a surge on all policies) With my check I purchased 1 TV, 2 computers, 1 Microwave, 1 refrigerator. I lost actual items, the items cost actual money I actually proved that they were lost to the insurance company, the company didn't care if/when I replaced any of them.
In any event I haven't read OP's documents relating to his mortgage, but I have personally written and closed a multitude of mortgages (plenty of them funded by OP's mortgage company) in my time, I have read thousands of Document packets, I'm sure that the mortgage company is with in their rights to require that the Home Owner maintain the property.
NOW could OP get a contractor and some other persons to write affidavits stating that the damage is not structural, that the home is not in disrepair and that the roof is still in livable condition then present this to the Mortgage Company and not fix the roof at all? Possibly... Op would need to speak with mortgage company on that, and possibly an atty if that is the route they would like to go.
-Source; Many years of mortgage exp.