Preheat the oven to 425 degrees F (220 degrees C).
Arrange carrots in an even layer on one side of a 10x15-inch rimmed baking sheet. (If you like, for easy cleanup, line pan with foil.) Drizzle carrots with oil and sprinkle with ¼ tsp. each salt and pepper; toss to coat. Roast 15 minutes. Meanwhile, for glaze, stir together apple jelly, honey, mustard, cinnamon, and ¼ tsp. salt in a small bowl. Sprinkle chicken with remaining ¼ tsp. each salt and pepper. Add apples in side of pan with carrots; drizzle with half of glaze and toss lightly to coat. Arrange chicken on other side; spoon remaining glaze over chicken.
Roast, turning halfway through, 10 to 15 minutes, or until carrots and apples are tender and an instant-read thermometer inserted into thickest parts of chicken registers 165°F. Drizzle with any glaze remaining in pan. Garnish with green onion and additional cinnamon.
