Most roof leaks need to be diagnosed be a professional roofer, common causes may be broken tiles, rusted valleys, worn lead flashing or deteriorated cement on the ridgecaps. Valleys are where two sections of the roof meet on different angles; they direct the water down to the gutters. Lead flashing can be replaced with new lead if needed; lead flashing can be installed in various parts of the roof where tiles do not completely seal against another surface.
The ridgecaps on a roof are the “v” shape tile that covers the sections where the tiles meet at a point on different angles. Ridgecaps are sealed onto the tiles with cement, if the cement is cracked and breaking away the ridgecaps will need re-bedding, which is removing the “v” shaped tiles and old cement and resetting with new cement. When the cement is still in fairly good condition it may not need to be replaced rather re-pointed with flexipoint. Flexipoint is a material similar to cement, the difference is that it isn’t as brittle and retains flexibility when cured, allowing it to flex with the roof without cracking or breaking away.