How can I ask the selling bank to fix the leaking roof of a REO before close?

I am almost ready to close a REO house. Home inspection identified the roof leaking problem. We have renegotiated the price for reroofing. But it is already the rain season. After a heavy rain this morning, I found a lot water from the leaking roof has soaked and penetrated the ceiling and damaged the laminate floor.
Our contract says sell AS IS. But my understanding is as the condition when it was shown to us. It shouldn’t be better, and shouldn’t be worse too. Right now it obvious has become worse.
I am asking for advice on how to dealing with this issue. Although I have got some credit on reroofing, I can’t do it until close the deal, which would be too late under current weather. Can I ask the selling bank to do some repair right now? If they decline our request, what could I do? What would be my right under this situation? Thanks a lot!