In a mixing bowl, combine the softened unsalted butter, minced garlic, chopped parsley, chopped rosemary, orange zest, kosher salt, and ground black pepper. Mix until smooth.
Rinse the chicken under cold water and pat it dry with paper towels.
Loosen the skin of the chicken and spread a generous amount of the butter mixture under the skin. Rub some on the outside as well.
Preheat your oven to 375°F (190°C). Place the chicken in a roasting pan, breast side up.
Roast for approximately 1.5 hours, or until the internal temperature reaches 165°F (74°C), basting every 30 minutes.
Once cooked, remove from the oven and tent loosely with aluminum foil. Let it rest for 15-20 minutes.
Carve the chicken into pieces and serve with your favorite sides.
Notes
Make sure the butter is softened but not melted for easy spreading. Use a meat thermometer to check the internal temperature accurately.