If the new roof shingles are of the same quality as the ones they replace, then you can claim it as a maintenance expense.

If the new shingles are significantly better than the old ones, then it would be a capital expense. If you are taking CCA on the building, you would add the cost of the shingle replacement there.

If you have TurboTax Live Assist & Review, here is how to talk to a Tax Expert: https://turbotax.community.intuit.ca/replies/3456106