Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Dice the sweet potato into 1/2-inch cubes and chop the broccoli into uniform bite-sized florets.
In a small bowl, whisk together the olive oil, lemon juice, minced garlic, rosemary, thyme, salt, and pepper.
Place the chicken breast, sweet potato cubes, and broccoli florets on the prepared baking sheet.
Drizzle the lemon-herb oil mixture over everything, using your hands or a spatula to toss the vegetables and coat the chicken thoroughly.
Arrange the chicken in the center and spread the vegetables in a single layer around it to ensure even roasting.
Roast for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the sweet potatoes are fork-tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep it juicy.