Storms come with high winds.  Roof leaks that happen during heavy rains "may indicate the end of the shingles life" both to the shingles, but many times a result of metal corrosion, and/or cracks in metal flashing.  Sometimes even just corrosion around fasteners can create enough space for water to leak during a heavy wind water travels or lifts tabs upwards allowing water in.  

Curled, and cracked shingles lead to absent shingles.   They have dried out much like an old asphalt driveway making them brittle and weak to stand up to winter weather and/or storms.   

Granules protect the asphalt from UV rays and also as a fire retardant.   No granules mean the asphalt will dry out, become brittle and start detaching from the roof.

It is likely caused by algae growing on your shingles.  Often appearing as dark streaks, roof algae is easily mistaken as wet patches.   The wet appearance of your roof could asl be caused by rotting shingles that are holding water for long periods of time. 

These are the places that typically have deterioration first.   Caught early it can be a very small fix.   It is important to inspect these areas frequently to remedy possible issues before the turn into bigger and costlier problems. 

Could be from a leak in roof, but also could be condensation from interior area having excess moisture levels.    Have us out to determine if its a leak:  

If it's not a leak, easy fixes can be; 

1-Dehumidifier

2-Extractor fan

3-Better ventilation in the room

4-Anti-condensation paint

Commonly caused by moisture that saturates the wood from behind the paint.   Meaning most times; this is a leaky roof.

The problem means there is liquid gathering behind the drywall or paint.   Take immediate action when this happens.   There's a chance the ceiling can collapse in the affected area.

The light could be coming from the ridge vent at the peak or possibly another type of vent.  If not a vent it is likely an animal chewed a hole and this needs to be repaired before water comes thru.

Sagging roofs are typically caused by insufficient or undersized rafters/trusses combined with excessive loads of weight.  Snow, ice, wind, and even too many layers of shingles can stress your roof and cause sagging.

If a leak or high condensation levels occur in the attic (the result of poor ventilation) the insulation can compress and become worthless.   Today's code is R-49; nearly 14"-19".   Have us provide a little more insulation in the attic with every new roof.  

Installing new fiberglass insulation pays for itself extremely quickly and keeps giving for years and years.