Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Dice the sweet potato into 1/2-inch cubes and chop the broccoli into bite-sized florets.
In a small bowl, whisk together the olive oil, minced garlic, dried rosemary, dried thyme, sea salt, and black pepper.
Place the chicken breast, sweet potato cubes, and broccoli on the prepared baking sheet.
Drizzle the herb oil mixture over everything, tossing the vegetables and coating the chicken thoroughly.
Squeeze the juice of half a lemon over the chicken and vegetables, then place the spent lemon half on the tray for extra aroma.
Roast for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the sweet potatoes are fork-tender.
Let the chicken rest for 5 minutes before slicing to keep it juicy, then serve alongside the roasted vegetables.