Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper.
Peel and dice the sweet potato into 1-inch cubes, and chop the broccoli and red bell pepper into bite-sized pieces.
Mince the garlic cloves and finely chop the fresh rosemary leaves.
In a large bowl, toss the sweet potato cubes with half of the olive oil, half of the garlic, and a pinch of sea salt and pepper.
Spread the sweet potatoes onto the sheet pan and roast for 15 minutes.
While potatoes roast, rub the chicken breast with the remaining olive oil, garlic, rosemary, sea salt, and pepper.
Move the sweet potatoes to one side of the pan, then add the chicken breast and the remaining vegetables to the other side.
Return the pan to the oven and roast for another 15-20 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender.
Remove from the oven and squeeze the fresh lemon juice over the chicken and vegetables before serving.