Position rack in lower third of oven; heat oven to 400°F.
Season chicken with 1 tablespoon chopped rosemary, ½ teaspoon salt and ¼ teaspoon black pepper.
In a bowl, toss squash with 1 teaspoon oil.
In a second bowl, toss onions with 2 teaspoons vinegar and remaining 1 teaspoon oil.
Coat a rimmed sheet pan with cooking spray.
Place chicken on pan bone side up; spread squash and onion in a single layer around chicken; sprinkle vegetables with remaining 1 tbsp chopped rosemary, ½ teaspoon salt and ¼ teaspoon black pepper; roast 15 minutes.
In second bowl, combine preserves, mustard, ginger, garlic and remaining 1 teaspoon vinegar.
Flip chicken and brush with apricot-mustard sauce; turn veggies; roast until chicken's internal temperature reaches 165°F, 10 to 15 minutes more.
Divide chicken and veggies among 4 plates; garnish each with a sprig of rosemary.
