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-inch pieces.
In a bowl, toss the sweet potato cubes with half of the olive oil, a pinch of sea salt, and a pinch of black pepper.
Spread the sweet potatoes onto the baking sheet and roast for 10 minutes.
While the potatoes roast, mince the garlic and finely chop the fresh rosemary and thyme.
Rub the chicken breast with the remaining olive oil, minced garlic, rosemary, thyme, and the rest of the salt and pepper.
Remove the baking sheet from the oven, push the potatoes to one side, and place the chicken breast on the other side.
Return the sheet to the oven and roast for another 18-22 minutes, or until the chicken reaches an internal temperature of 165°F.
While the chicken finishes, steam the broccoli florets in a steamer basket for 4-5 minutes until bright green and tender-crisp.
Plate the chicken and potatoes, serving the broccoli on the side, and finish with a fresh squeeze of lemon juice over the entire dish.