Preheat oven to 375 degrees F.
Pat the turkey dry with paper towels.
In a small bowl, combine the softened butter, chopped fresh rosemary, and minced garlic.
Very gently lift the turkey skin from the breast (do not remove it completely) and rub the herb butter evenly under the skin.
Drizzle 1 tablespoon olive oil over the turkey breast and season with 2 teaspoons kosher salt and 1 teaspoon black pepper.
Place the turkey on a half sheet pan and par-bake: 15 minutes if completely thawed, 20–25 minutes if partially frozen, or 30 minutes if fully frozen.
Clean and dry the sweet potatoes (do not peel).
Pierce each sweet potato about 10 times with a fork.
Par-cook the sweet potatoes in the microwave for 4 minutes, flipping them after 2 minutes.
Drizzle the par-cooked sweet potatoes with 1 teaspoon olive oil, sprinkle with 1/2 teaspoon kosher salt and black pepper, then wrap each potato in aluminum foil and set aside.
In a large bowl, whisk together the beaten egg and 1/2 cup chicken stock until combined.
Add the stale sourdough bread cubes, chopped carrot, chopped celery, chopped shallot, 2 tablespoons melted unsalted butter, 2 tablespoons olive oil, 2 minced garlic cloves, minced thyme, minced rosemary, minced sage, and salt and pepper to taste; toss gently to combine, taking care not to break the bread cubes.
Set the stuffing mixture aside to allow the bread to absorb the liquid (about 10–30 minutes, see notes).
Clean, trim, and pat the green beans dry.
Toss the green beans with 1 tablespoon olive oil, 2 minced garlic cloves, and salt and pepper to taste; set aside.
Increase oven temperature to 400 degrees F.
Remove the turkey from the sheet pan.
Spread the stuffing in a single layer no larger than 1" on one side of the sheet pan and place the wrapped sweet potatoes on the other side.
Return the turkey to the remaining space on the sheet pan and bake for 30 minutes.
Remove the sweet potatoes from the oven, slice each lengthwise and place cut side up on one quarter of the sheet pan.
Gently scrape the inside of each sweet potato to create a well.
Combine 3 tablespoons melted unsalted butter, 1 tablespoon maple syrup, and 1 teaspoon ground cinnamon and drizzle over the cut sweet potato halves; top with 1/4 cup toasted pecans (if using) and 1/2 cup mini marshmallows.
Stir the stuffing and place the turkey breast on top of the stuffing on the sheet pan.
Place the prepared green beans on the remaining quarter of the sheet pan.
Bake for an additional 20–25 minutes, or until the turkey is golden brown and an instant-read thermometer inserted into 2–3 different places reads 165 degrees F.
Remove the pan from the oven, set the turkey aside while you plate the sides, then slice the turkey and serve immediately.