Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Peel and dice the sweet potato into 1-inch cubes, slice the carrots into rounds, and halve the Brussels sprouts.
Mince the garlic cloves and place them in a small bowl with the olive oil, rosemary, thyme, sea salt, and black pepper, whisking to combine.
Place the chicken breast and the chopped vegetables on the prepared baking sheet in a single layer.
Drizzle the garlic-herb oil mixture over the chicken and vegetables, tossing the vegetables and coating the chicken thoroughly.
Roast in the oven for 25-30 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and caramelized.
Let the chicken rest for 5 minutes before slicing to ensure it stays juicy, then serve alongside the roasted root vegetables.