Pat dry a thawed raw chicken with paper towels and place into a greased 9x13 baking dish.
In a bowl, mix together the butter, 2 tablespoon of fresh chopped rosemary, 1 teaspoon of salt, ½ teaspoon black pepper, ½ teaspoon garlic powder and ½ teaspoon onion powder until blended.
Rub the chicken with the butter mixture and get some under the chicken on the breasts too. This will help to really enhance the flavor and juiciness of the chicken!
Inside the chickens cavity, place a quarter of an onion, 2 carrots sliced down the middle and in half length wise and halved celery stalks. Try to pack them in there as best as you can, but it's okay if it doesn't all fit.
Wash your baby carrots and your potatoes. Quarter the potatoes or cut them into 1 inch sized cubes (whichever is smaller).
In a large glass bowl or gallon sized-ziploc bag, mix the carrots, potatoes, and remaining seasonings (½ teaspoon salt, ¼ teaspoon black pepper, ½ teaspoon garlic powder, ½ teaspoon onion powder) as well as 3 tablespoon of olive oil.
Place the potato and carrot mixture around the chicken in the pan.
Bake in the oven for 30 minutes and then reduce the heat to 375 degrees F for 40-50 minutes or until the chicken registers 160-165 degrees F with an instant read thermometer and the potatoes are fork tender.
Allow to cool for about 10 minutes before slicing. This will allow the chicken to finish cooking and will help to retain more of the juices so they don't spill out onto your cutting board. Be careful as the chicken will be hot.
Notes
Ensure the chicken is fully thawed before cooking to avoid uneven cooking.
Place the butter mixture under the skin for crispy skin and juicy meat.
To prevent wing tips from darkening, tuck them into a small slit above the thigh.
Store leftovers in an airtight container for up to 5 days. Reheat before serving.