How repair stone on roof?

This is not stone, it is a pre-cast concrete corbel. To carry out a proper repair, the brickwork above should be removed, and the concrete corbel replaced with a new corbel, which should be available from a merchant or specialist supplier. It wouldn’t be satisfactory to simply repair the existing corbel as there is movement in the brickwork above.

Iv seen ya video , think that's just because of the weather don't think its hurting anything

Strip down and rebuild as it will eventually corrode fall off and possible kill someone if hit hope it helps

It's a huge job to break out the concrete stone that is only cracked sheared on corner where it over sails (corbel). You'll damage allot of the surrounding brickwork where it could end up an unnecessary BIG task. Why not break off the spalled cracked concrete & if the steel reinforcement exposed treat with red oxide + primer coat 6-10 & then carry out concrete repair in scratch coat layers of HB render roc / fosroc 615 until flush with existing face. This will be cost effective too.