One sign that you roof might have been compromised is staining on the ceiling. Is there any warping of the sheet rock or light brown staining? If so, that is a good indicator that their might be a leak. Also, if the taping between the sheet rock is coming apart their could be moisture present. There could also be a foundation problem if you see separation, but that's a whole different beast. Mold is another indicator of a roof leak. It could be a problem if left alone and not addressed in a timely manor.
The number one cause for a roof leak is found in the flashing around the roof penetrations. The term roof penetrations refers to things like the exhaust vent (from the water heater), attic vent (wind turbines or box vents), and typically the plumbing vent.
(Examples of roof penetrations)
Typically, the flashing (basically the shield around the roof penetrations) on the plumbing vents is the cause for your leak. Those plumbing vents are their for the stench from your toilet to escape and they usually have rubber flashing. The problem with rubber flashing, especially here in Texas, the rubber deteriorates at a faster rate. The first thing we look at on a roof when the homeowner is concerned about a leaky roof is the flashing around plumbing vents (because it's almost always the culprit).
We typically like to use lead flashing when it comes time to replace. It doesn't rust and it lasts a lot longer than rubber. Most companies will use rubber (because it's a lot cheaper), but when you use lead flashing instead, it lasts 50 years instead of 5. That's just one of the things that make us different.
The sooner you address the leak the better. Don't let damage more of the sheet rock. If left unaddressed you could develop mold or the rafters could rot. Guardian Exteriors can do a free assessment for you. Get piece of mind today.