Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel the sweet potato and dice it into uniform 1-inch cubes to ensure even roasting.
Trim the woody, tough ends off the asparagus spears and set them aside.
Finely mince the garlic cloves until they form a paste-like consistency.
In a small mixing bowl, whisk together the olive oil, minced garlic, dried thyme, dried rosemary, sea salt, and black pepper.
Place the chicken breast, sweet potato cubes, and asparagus spears on the prepared baking sheet in a single layer.
Drizzle the garlic-herb oil mixture over the chicken and vegetables, using your hands or a brush to ensure everything is well-coated.
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 sweet potatoes are fork-tender.
Remove from the oven and immediately drizzle the fresh lemon juice over the chicken and vegetables to brighten the flavors before serving.