Do you really mean rock? Or clay?
You can tell if it's clay because when wet, clay becomes very sticky. 'Rocks' cannot normally be broken very easily. When clay is dry it might appear like rock. Or could it be compacted hardcore, or builders' rubble?
Gardens that are on clay do exhibit the property that you can dig down through the topsoil to about a spade's depth, and then you meet a layer of clay, which may appear solid. Clay can, in principle, be excavated and 'improved', but that's a very big job. Roses will grow down through clay. Many people grow roses satisfactorily on clay without going to all the trouble of trying to excavate or dig through the clay.