Basically correct (except the concept of volume doesn't hold up in a black hole). It is theoretically possible to have a black hole big enough that its Roche limit is inside its event horizon; but a black hole that big is probably at least vanishingly rare in the observable universe.
A black hole has a volume less than it's event horizon. So, it's not really undefined as much as ill defined. Also, a black hole's event horizon is not necessarily a perfect sphere ex: two black hole's orbiting each other.
