Preheat broiler. Place sweet potato wedges and the water in a microwave-safe baking dish. Cover with plastic wrap; vent plastic wrap to allow steam to escape. Microwave on 100% power (high) for 6 to 8 minutes or until sweet potatoes are nearly tender, rearranging sweet potatoes once halfway through cooking. Drain well.
Meanwhile, in a small bowl, combine mustard, honey, olive oil, rosemary, and pepper; set aside.
Place sweet potatoes on the greased unheated rack of a broiler pan. Broil 3 to 4 inches from the heat for 3 to 4 minutes, carefully turning once with a metal spatula. Brush with half of the mustard mixture. Broil for 2 to 3 minutes more, turning and brushing once with remaining mustard mixture.