How would I separate uncooked rice from salt rocks?

Mixing the 3 with water would dissolve the salt. Filtration would then yield salt water and a rice/pepper mix on the filter. Evaporation of the salt water would afford dry salt. THe other two are harder being organics - trial and error might lead you to a solvent that would dissolve pepper, but not rice or vice-versa. Filtration and evaporation could be used again, but I have no idea about which solvent to use.

To use chromatography you would need a solvent for all three or a sequence of solvents to sequentially dissolve each component.