The rock generally used for roofing, is

ANS:C - slate

Slate can be made into roofing slates, which are installed by a Slater. And, are a type of roof shingle, or more specifically a type of roof tile. Slate has two lines of break ability "Cleavage and grain" which make it possible to split the stone into thin sheets. When broken, slate retains a natural appearance while remaining relatively flat and easy to stack.