In a large bowl, stir together the olive oil, rosemary and 1/4 teaspoon salt. Add the sausage, fennel and apples and toss to coat.
Position a rack 5 inches beneath the broiler; preheat. Thread the sausage, fennel and apples onto metal skewers; arrange on baking sheets in a single layer. Broil, turning once, until lightly browned, 10 to 15 minutes.