Preheat an oven to 400 degrees F.
Select a 2-inch deep casserole dish that is large enough to hold the shrimp in a single layer. Add the rock salt to form a 1-inch bed in the dish. Slide the casserole dish into the oven and heat for 30 minutes.
Add the minced garlic and olive oil to a mixing bowl to prepare the marinade.
Make an incision down the back of each of the shrimp. Devein or remove the intestine from each piece and add the shrimp to the marinade. Toss together to coat, and let the ingredients rest for at least 10 minutes.
Once heated, pull your casserole dish from the oven and arrange the shrimp on the bottom in 1 layer. Return the dish to the oven, and roast for 2 minutes. Turn each shrimp over, and set them aside to let the residual heat from the pan finish cooking their second sides. Serve warm.