I'm sorry but I have a hard time with that logic. We could sell as-is and maybe make nothing. Or we could put a $4,000 roof on and perhaps make $35,000. Seems like an easy decision.
In an ideal world, sure. So assuming you choose to replace the roof:
1. What is your plan for borrowing the $10K to replace the roof?
2. What is your plan to pay the @$4K in property taxes due next month?
3. What is the carrying cost of borrowing another $14K for several months, which would presumably be at 25-30% interest, and delaying paying down your high-interest debts for that period?
4. How confident are you that roof + sale = $35K? You can't know how much the roof is going to cost until you get quotes; I suspect the exposed plywood means the repairs will cost more than you hope. And if you're relying on a single real estate agent's valuation, well, let's just say they have been known to exaggerate to get business.
None of your choices have changed since last month, and they aren't going to change (for the better, at least) in another month. So if you have already decided that you don't want to sell until you replace the roof, it's past time to get quotes and look into financing.
Honestly, my impression from reading these threads is that you are still stuck -- you know you need to do something, but you are still thinking the way you have always thought, and so all of the reasons why you don't want to sell keep coming back up and hitting you in the face. But look at where that thinking has gotten you: into massive debt, borrowing money at purely usurious interest rates (30%!) to fund your lifestyle, all the while with one of your primary "assets" at such risk that no insurance company will insure it. You can't trust the thinking that got you into this kind of position -- you can't fixate on the two birds in the bush when the one you think you have in hand is actually a live grenade.
Sell something. Now. Put the rental on the market as is, today. In the meantime, get quotes for a new roof, and figure out financing, so you can do the actual math (including March taxes + carrying costs of delaying the sale until after the repairs are done). If you don't get a decent offer as is, you can always pull the house from the market and re-list once the roof is done. You have choices -- you just need to make one.