Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Wash and peel the sweet potato, then dice it into uniform 1-inch cubes. Mince the garlic cloves finely.
In a small bowl, whisk together the olive oil, minced garlic, rosemary, thyme, sea salt, and black pepper.
Place the sweet potato cubes on one side of the prepared baking sheet and toss with half of the garlic-herb oil mixture.
Pat the chicken breast dry with a paper towel and place it in the center of the baking sheet, rubbing the remaining herb oil over both sides.
Roast the chicken and sweet potatoes in the oven for 10 minutes.
Carefully remove the pan and add the broccoli florets to the empty side, tossing them slightly in the juices on the pan or a tiny splash of water.
Return the pan to the oven and roast for an additional 12-15 minutes, or until the chicken reaches an internal temperature of 165°F and the sweet potatoes are fork-tender.
Remove from the oven, drizzle the fresh lemon juice over the chicken and broccoli, and let the meat rest for 5 minutes before slicing.