I am a few days to closing escrow and I discovered the roof shingles are coming off! What options do I have?

The owner did not state anything wrong with the roof in disclosures, but my home inspector noted the roof needed repairs in a rear area. Owner agreed to repair but now large parts of shingles during a wind storm came off in the front of the home! I need to know is this a reason to postpone escrow, and if the owner refuses to fix the whole roof and amend purchase price can I pull out of deal without loosing my down payment?