Putting Salt Water "Live Rock", that has been in a salt water circulating system, then putting them into a fresh water environment will kill off anything that was living on them in the salt water.
Be looking for a super ammonia spike when that happens.
I had a friend who did that same thing, and they paid the price for that error, lost all their livestock with the super ammonia jump. It took several weeks, to 3 months, to get that tank back into equilibrium after that. They didn't have a clue as to why, until we told them the reason.
And like the others stated, "Home salt" or kitchen salt is a NO NO in the tank. Use only REEF, Sea, or Ocean pre~made SALT for Salt water aquariums, and for Fresh water, use ONLY Aquarium FW or Kosher salt like tabMorte stated.
Live rock isn't really "Alive", it has bacterial colonies that grow on its surfaces, that help filter the water. WHAT DOES IT NEED? Good Water Circulation, and light, depending on what you want it to grow. Algae needs light, bacteria need circulation.
Remember, SALT does NOT evaporate out. It must be manually TAKEN OUT with water changes, and if you change out only 80% of the water, and replace 100% of the FW Salt for the tank's capacity, then you will, in time, end up with a tank full of salt. Only replace with the exact prescribed amount of salt for the water you plan on
putting back in the tank.