Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Peel and chop the sweet potato, carrots, and parsnips into uniform 1-inch bite-sized cubes.
In a large mixing bowl, toss the root vegetables with half of the olive oil, half of the chopped rosemary, sea salt, and black pepper.
Place the chicken breast on the prepared baking sheet and rub with the remaining olive oil, minced garlic, and the rest of the fresh rosemary.
Spread the seasoned root vegetables in a single layer around the chicken breast on the baking sheet.
Roast in the center of the oven for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and golden brown.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep it juicy.
Plate the sliced chicken alongside the roasted vegetables and serve immediately.