PREHEAT: Position a rack in the center of the oven and preheat the oven to 400ºF. Line a baking sheet with heavy duty foil, and a sheet or parchment paper for easier clean up.
SEASON: In a bowl, combine the melted butter with black pepper, ½ teaspoon paprika, 2 teaspoons minced garlic, ½ teaspoon onion powder, ½ teaspoon Italian seasoning, 1 teaspoon kosher salt, 1 tablespoon rosemary, and lemon zest. Set aside 1 tablespoon of this mixture for green beans. Loosen the skin on the chicken and gently rub the remaining mixture all over and under the skin. Place chicken on the baking sheet.
POTATOES: Add potatoes to a bowl. Toss with avocado oil, remaining ½ teaspoon paprika, 2 teaspoons minced garlic, ½ teaspoon onion powder, ½ teaspoon Italian seasoning, 1 teaspoon kosher salt, and 1 tablespoon rosemary. Give it a good mix before you add potatoes to the baking pan.
ROAST: Roast chicken and potatoes for 35 minutes. Check chicken for doneness using a meat thermometer. Remove any chicken pieces that have reached 165ºF, if done, or move them to one side and tent loosely with foil if it’s browning too quickly but hasn’t cooked through.
TOSS BEANS: Add green beans to the same bowl as the potatoes. Toss them in the reserved tablespoon of butter mixture.
FINISH: Place beans on sheet pan with the potatoes. Cook for 10 minutes or until the chicken is cooked through to 165ºF and the potatoes are tender. The green beans should be just past al-dente as well by then. Remove sheet pan from oven. Let cool for several minutes before topping with parsley and serving.