Place the beets in a large mixing bowl, and the carrots in a 9 inch by 13 inch glass baking dish. (Mixing the roots separately keeps the carrots from turning pink from beet juice.)
Place the butter or ghee in a microwave-safe coffee mug and add the garlic. Microwave until the butter is melted. Stir in the dried rosemary.
Pour half of the melted butter mixture over the beets, and pour half over the carrots. Sprinkle generously with sea salt and freshly ground black pepper. Toss each of the root vegetables to coat them with the butter mixture.
Dump the beets into the baking dish with the carrots.