Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel and cube the sweet potato into 1/2-inch pieces, then toss them on the baking sheet with 0.5 tbsp of olive oil and a pinch of salt and pepper.
Roast the sweet potatoes for 10 minutes to give them a head start on caramelization.
While the potatoes roast, mince the garlic and combine it in a small bowl with the remaining olive oil, rosemary, thyme, salt, and pepper.
Pat the chicken breast dry with a paper towel and rub the garlic-herb oil mixture evenly over all sides.
Remove the baking sheet from the oven, push the sweet potatoes to one side, and place the chicken breast and broccoli florets on the other side.
Return the sheet to the oven and roast for 18-22 minutes, or until the chicken reaches an internal temperature of 165°F and the broccoli is slightly charred.
Remove from the oven, drizzle the lemon juice over the chicken and broccoli, and let the chicken rest for 5 minutes before slicing and serving.