Soak them in about 25% clorox for a couple days and then rinse, rinse, rinse... until you dont smell bleach anymore and let them dry out. But only if you want to kill whatever is on the rock.
I don't understand why you would do this. Rock will absorb chlorine and you will never be able to rinse it off. If you are starting over, dead things will turn into ammonia and start the cycle. By the way sorry about your loss. I got my rbta from you and my clowns enjoy it very much.
Kevin
Bleach using what?
This sounds like what happened to me last summer. Came home to a cooked nano. All I did was pull out the coral and fish that died... Left everything else alone and my tank was back and ready in 3/4 weeks. Now it's back as if it never crashed. Leave your rock and sand alone. Do a huge water change and wait.