To determine if your roof needs replacement or repair with aluminum sheets, look for the following signs: visible rust or corrosion, especially on the seams and fasteners; sagging or buckling in the roof surface; leaks or water damage inside your home; and excessive noise during rain or wind. If the damage is widespread or the roof is old, replacement might be necessary. However, if the damage is limited to specific areas, repairs could suffice. It's always best to consult with a professional roofer for an accurate assessment.