If you have water stains on the ceiling or running down the walls these are usually signs of roof leaks. The hard part is finding where the leaks are coming from. if you have a roof leak it needs to be fixed asap. A leaking roof can cause mould, wood decay to rafters & ceiling timbers as well as plasterboard ceilings, furniture & flooring. Leaks usually originate away from where they appear. Water typically comes in through broken tiles, worn/corroded or poorly sealed flashing, skylights, chimneys or vents.
Once the water passes through the roofing is flows along roof rafters, sarking until
it finds a place to drip down.
Looking for a roof leak is best done during the day, garb a ladder & get into the roof void take a torch with you. Step only on secure framing timbers not on the insulation or the ceiling boards, as these will not support your weight.
Start at the point where the leak was found & work your way up roof looking for wetness along the framing timbers. If the weather has been dry for some time look for staining or discoloration on the timbers/tiles, then turn your torch of & look for holes/cracks & daylight thru these areas. You found the point of entry now can you fix it easily or do you need a roofing expert assess the situation & proceed with the best option.