Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Peel and dice the sweet potato into 1/2-inch cubes to ensure they roast evenly.
In a small bowl, whisk together the extra virgin olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper to create the marinade.
Place the chicken breast and diced sweet potatoes on the prepared baking sheet, then drizzle with three-quarters of the lemon-herb marinade, tossing well to coat.
Roast in the center of the oven for 15 minutes.
Remove the pan from the oven, add the broccoli florets to the tray, and drizzle with the remaining marinade.
Return the pan to the oven and roast for an additional 10 to 12 minutes, or until the chicken reaches an internal temperature of 165 °F and the vegetables are golden and tender.
Let the chicken rest for 5 minutes before slicing and serving with the roasted vegetables.