There is a separate safe harbor for improvements that applies to small landlords, that would allow you to deduct the cost all at once, it is limited to items that cost 2% or less of the building's value or $10,000. So that probably doesn't help you either.
https://www.irs.gov/businesses/small-businesses-self-employed/tangible-property-final-regulations#Wh...
Note that if you depreciate over 27.5 years but the shingles need to be replaced again earlier, the remaining depreciation can be claimed at that time. (i.e. if the roof becomes unserviceable and needs to be replaced after 15 years, you can deduct the remains 12.5 years of depreciation then. If the roof lasts 20 years, you deduct the remaining 7.5 year when you replace it. And so on.)
