Cut squash in 1/2 cut then into 1/2 inch slices, cut mushrooms in 1/4, cut onion into 1/2 inch wedges
Preheat over to 400. Combine squash, mushrooms, onions, garlic in roasting pan season with Salt & Pepper and olive oil cook for 15 minutes.
While veggies are cooking. Lift the skin rub the flesh with olive oil, rosemary, salt & pepper. Place chicken on veggies skin side up and place roasting pan back in the oven for 40 min to 1 hour (depends on the thickness of the chicken). Until veggies are tender.