You can on the AC if it cost less than $2,500 (which if it's central air, I doubt), but not the roof. Both assets are classified as residential rental real estate and depreciated over 27.5 years.
I seriously doubt claiming the SDA it will make one single penny of difference to your 2020 tax liability. However, it will hurt you big time if you sell the property prior to the tax year when you would have reached the bonus depreciation level, without taking the SDA.
When you add up the deductions of mortgage interest, property taxes and property insurance and add to that the depreciation you're required to take each year by law, those four items alone are usually enough to exceed your total rental income for the tax year. Add to that your other allowed rental expenses (repairs, maintenance, etc.) and you're practically guaranteed to operate the rental at a loss every single year.
With the change in tax law in 2018 that allows you to deduct up to $25K of rental losses against other ordinary income if you are actively involved in the rental activity, it "might" help now. But again, if you sell early then having to recapture all that depreciation can hurt. Depending on your overall income and the sales gain in the tax year you sell, the recaptured depreciation could be enough to bump you into the next higher tax bracket, if your gain on the sale doesn't do that by itself.
