Damaged or Missing Shingles
Intense weather is usually not a good friend of shingles. Strong winds or heavy rains cause shingles to loosen up and fly off. +15 year old roofs are the ones who suffered more from this, as they may naturally already been loosening up for a while because of their age. Which is usually what causes cupping and curling.

If the center of the shingle is concave, the shingle is cupping. If the edges become turned up, they are described as curling. Both scenarios are a clear indication you need a roof replacement.

These you can easily find when they show up at one of the rooms or you can search for them in your attic.

When examining the roof from inside your home, if you notice any gaps where the summer sun is filtering through the roof boards or see any watermarks, that’s a clear sign you need a roof repair or replacement.

This is one of those silent kill signs. When left untreated, moss can spread and create large patches that hold water against the surface of the roof. This causes the roofing materials to rot, create leaks and even obstruct gutters.

Visual Deterioration
When your roof is no longer that shiny nice color you chose, you can tell. Old roofs do not display their color as they once did due to intense sunlight, snow, rains, winds, etc. As well, rotting can help when powered by moss.

Missing Flashing
Flashing is the material placed around objects that protrude from roofs, such as your chimney and roof vents. It is designed to prevent the movement of water into your roof by averting the water away from seams where water runoff is greater.

So, check around walls, dormers and chimneys for any leaks or damaged material where water can penetrate.

The top of your roof should follow a straight line along the ridge. If there is a saddleback or sag in the middle, it may be a warning sign of structural damage and might cause your roof to collapse if not detected and treated early.

Sagging can be caused by frequent exposure to moisture and a vast amount of water, faulty roofing material or improper installations despite high-quality materials.