If you don't know how your stones will be have at temperature, test them -- in a strong saggar in case they explode -- even at bisque stage. Test samples of the stones alone in the saggar, or make test pieces with the test stones that won't upset anyone if there is a failure. That's a good rule of thumb for introducing any unknown material you're putting in the kiln.
The question can be if you have specific stones you want in your work or just want the illusion of rocks? You can always make stones from clay and embed them in your work, It reduces the issues of shrinkage fit. For contrast, use different clay bodies for the "stones" to give different textures, but use something close to the same shrinkage factor. Also play with colorants in your clay "stones". Just use caution when using chemicals and handling with bare hands and surface/tool clean-ups. And if your faux "stones" are large, remember to dry thoroughly and add steam holes as necessary.
A friend once did a study of hollow logs and bird nests, including making many realistic stones and pebbles and bird eggs. With not a lot of effort on the stones, those who didn't watch her endlessly roll and decorate these lumps (She made a LOT of them), would swear she used real rocks in her prices. One errant pebble actually got away and rolled into one of my mugs in a firing. Fortunately, with the way the glazes laid, it was still perfectly functional, but looked like a speckled rock was lodged in the bottom.