Preheat your oven to 425°F (220°C).
Peel (if desired) and cube the sweet potato into bite-sized pieces. Place them on a baking tray.
Drizzle 1 tsp of olive oil over the sweet potato cubes, and season with a small pinch of salt and black pepper. Toss to coat evenly.
In a mixing bowl, place the chicken breast. Drizzle the remaining 1 tsp of olive oil over the chicken.
Finely mince the garlic and chop the fresh rosemary. Add them to the chicken along with a pinch of salt and black pepper. Rub the seasoning onto the chicken breast.
Place the seasoned chicken breast on the same baking tray or on a separate tray if preferred. Arrange the sweet potatoes around the chicken.
Roast in the preheated oven for 25-30 minutes, or until the chicken reaches an internal temperature of 165°F and the sweet potatoes are tender and slightly caramelized.
If a crispier finish is desired, broil for an additional 2-3 minutes, watching closely to avoid burning.
Remove from the oven, let it rest for a few minutes, and serve warm.