No, the rock salt is quite different from epsom salt. Rock salt is made of NaCl and Epsom salt is Magnesium sulphate. Epsom salt has formula MgSO4. 7H2O. It is basically a hydrated salt. Rock Salt is mostly used for food processing and preparing, and in cosmetics. But Epsom salt has fewer usages in these areas. Epsom salt is used in medication area, laboratory reactions,etc. Epsom salt crystals are larger than table rock salt crystals.
Salt which is used in cooking is known as sodium chloride. But when we talk about Epsom salt, it is a unique type of salt which is made up of magnesium and sulphate. Rock salt is a form of salt which is processed less and has larger crystals and these take longer time to dissolve. Rock salt is the same sodium chloride which is used in basic cooking food. Rock salt is different from epsom salt. Rock is a form of table salt but epsom salt can never be table salt or can be used in cooking food.