I would like to use partial disposition (old roof is currently depreciated as part of the entire property) or casualty loss for the old roof for 2022 taxes.
If the old roof was not listed as it's own individual asset, then you can't do what you want. If you change the cost basis of the property asset (which includes the old roof) you will totally screw up the depreciation history, as well as future depreciation going forward. Leave it alone unless you are prepared for an audit which you will most likely. lose.
If I add a new asset it restarts the depreciation at 27.5 years which does not seem right.
It is exactly right. Depreciation on the new roof starts on the date it was placed in service, for a period of 27.5 years from that date. Typically, this is one day after the work is completed, assuming the property was classified as a rental while the work was being done.
