Working on a race of rock people who live in a fantasy setting. Realistically, how would they obtain energy (do they need to eat? breath?) and how could they reproduce or perform other biological processes?
If they are rock people, as in creatures made entirely of rock, then they wouldn't require energy. They would basically be magically animated constructs. In this way, they could "reproduce" by animating other rock.
If you would rather them be biological with a rocky shell, then that can be done many ways. You could take the simple approach of having them be like an organism on Earth, but with a rocky exoskeleton, skin, or shell. Or, you could try creating a biological creature different than one on Earth that incorporates a rocky carapace. In this way, they could reproduce like biology we know (sexual or asexual), and could have methods of removing their shell, if you couldn't find a way around it.
If you want them to be rocky, but not biological, yet still requiring energy, you could either make them able to gain energy magically, or you could have their shell absorb energy in some fashion. A porous rock would allow liquids to get in, so many they have mechanisms that can get nutrients from certain liquids. Or, you could have metal shells that are conductive, allowing them to absorb heat or electricity. This could be intriguing, as cold could possibly be a weakness for them. In this way, as they aren't biological, they may not be able to reproduce. But you could also have them unable to die, as they aren't living. They can only be destroyed. Otherwise, magic could let them make more of themselves.