Have you tried to find a hole or a leak in the roof which is causing moisture or water build up inside the house but still think that there is something that you are missing to check or a corner of the roof that you are missing to check. Sure, the roof of a house is responsible to keep rain water out of the house, but that is not the only source of water or moisture build up in the house.
It might be time to check for other sources like plumbing issues and condensation due to humidity. Checking for plumbing leaks is easy, turn off the all water taps, valves and any other water feature like fountains and aquarium water supply and head to the water meter. If you see it running up then you know it is time to call a plumber to find the leak and fix it.
Finding a condensation spot can be a bit complicated. Here is how condensation can happen in your house, for example you have an AC duct passing next to the chimney. Now since the area around the chimney could be warm the humidity around the a/c duct will result in condensation and lead to water dripping from the duct, drop by drop the water will drip on to the insulation and walls which will absorb it and result in visible wet patches.
Another common area where humidity is high is the attic and this can also result in condensation during winters. To avoid condensation it is important to conduct timely air quality checks and also get the house insulation checked.