@Festivabob
You would create a new asset for the replacement roof with a cost equal to the difference between the total cost and the amount of the insurance reimbursement, probably your deductible. You must also apply the appropriate percentage for the home office.
Basically, you can deduct the home office percentage of home maintenance expenses that benefit your entire home, such as housecleaning of your entire house, roof and furnace repairs, and exterior painting. These costs are deductible whether you hire someone or do them yourself.