1. Note what's happening
Record where and when the issue shows up, protect the space if that's safe, and pull together whatever roof history exists.
2. Check the whole assembly
Deck soundness under decades of lake-effect snow load, ice-dam history at the eaves, ventilation balance, and valley and penetration flashing -- not the shingle brand -- point toward repair or full replacement.
3. Write the scope down
Lay out prep, protection, materials, permits, testing, cleanup, restoration, and how changes get priced.
4. Compare bids on substance
Verify credentials, then weigh the reasoning behind each proposal against the others.
5. Confirm the closeout
Testing, cleanup, documentation, and warranty terms should all be handed over before you call it done.