Preheat convection oven to 350F
In a mixing bowl, mix softened butter, salt, pepper, and sage
With your hand loosen skin above chicken breast
Rub butter mixture inside and outside chicken
In a roasting pan place quartered onions, halved carrots, celery and garlic cloves
Place chicken, breast side up, on bed of vegetables.
Stuff cavity of chicken with onion, carrots, and celery
Place sprig of rosemary into each leg of chicken
Baked for 50-60 minutes, until chicken is golden brown.
Let chicken rest for 10 minutes before cutting into pieces
Serve in sections (legs, thighs, breast) with roasted carrots as a side