If this is a short sale, you should already have a ratified contract. The contract is between you and the seller - the bank comes into the picture because the seller will short the payoff to their mortgage holder and that bank (or banks) approves or disapproves the agreed upon contract terms. That is a contingency of the sale, but they do not sign the contract.
You should consult with your agent and ask her to work with the listing agent in getting any answers from the bank. The short sale negotiation between the bank and the negotiator could easily take 4-6 months or more before an approval is issued. Your agent will help you with your options if the condition of the property worsens during the process. Good Luck!
The bank response time varies in terms of either, accepting your offer or countering. The terms of the contract will dictate who is responsible for what. If it is a short sale the seller still owns the home.
Good luck and I hope you have a speedy response.
Your contract should spell out the terms of property condition. Did your offer for the home contain an "as-is" clause? Your Realtor should be able to guide you on the terms of your specific contract. If this is really your house and the roof leak can be mitigated by something inexpensive (like tarping it), that might be worth your while.