Roof leaks in clay or concrete tiles:
When walking on a clay or concrete tile roof place all of your weight on the very front edge of the tiles as it is under this that the timber battens holding them up are. Locate the cracked or broken tiles and slip the claw of a hammer up under the row above just off to the left side of the tile to be removed. Then pull out this tile and slip in the new one. And pull the hammer out to finish.
Sometimes it is necessary to repair a tile with a masonry grade silicone sealant in position. In these cases you must seal down both sides of the tile being sealed as well as the crack itself.
Also sometimes silicone is very useful if there is a crack in the ridge capping or the mortar work.
However the best way to repair the ridge capping is by mixing up 6 parts sharp sand to 1 part cement plus water. And after gently lifting the loose ridge capping run a new bed of mortar and reposition them and run a steel trowel down the sides to finish.