Can I just fix my hood and keep the money for the roof?

The answer depends on if you have a loan/lien holder on your vehicle.

Yes – you can, IF… you have COMPLETELY paid off your vehicle.  If the car belongs to you–without any loans or liens against it–you can keep the money and fix any portion; or nothing if you like.

(The insurance company’s obligation is to come to an agreement with you and to compensate you for the damage that is involved in the claim.)

NO – not if you still owe money to the bank for your vehicle.   If you still owe money on your vehicle and and recieved a check from an insurance claim, then you MUST fix your vehicle, or let the bank keep the check.   Only fixing part of the vehicle could be insurance fraud or a violation of your loan agreement.