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No, you would not complete the Dispositions section of the Asset Worksheet. The old roof is included in the basis of the building, so you adjust that asset rather than disposing of the old roof. This is the entry you make on Line 4.

Unless this is the first year you've owned this property, you should have Prior Depreciation on the report. I'll attach a screenshot of the 2021 TurboTax Form 4562 Depreciation report to show which column you need.

Line 10 Prior Depreciation in my example would be the Adjusted Accumulated Depreciation = $3,150.

For Line 12, you will need to refer to the 2021 AMT Depreciation Report (see screenshot #2) from last year. There will be an amount for Prior Depreciation on that report. Reduce that amount by the same amount you used for Line 10, then enter the result on Line 12.