Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel and dice the sweet potato into 1/2-inch cubes and slice the carrots into 1/4-inch thick rounds to ensure they roast evenly with the chicken.
Finely mince the garlic cloves and strip the rosemary leaves from the stem, chopping them finely to release their oils.
In a large mixing bowl, combine the chicken breast, diced sweet potatoes, and carrots.
Drizzle the olive oil over the mixture and add the minced garlic, chopped rosemary, sea salt, and black pepper, tossing thoroughly to coat every piece.
Spread the chicken and vegetables in a single layer on the prepared baking sheet, making sure not to crowd the pan so the vegetables can caramelize rather than steam.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the root vegetables are fork-tender.
Remove from the oven and let the chicken rest for 5 minutes before serving to ensure it remains juicy and tender.