Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
Cube the sweet potato into 1-inch pieces and chop the broccoli into bite-sized florets.
In a small bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, dried oregano, sea salt, and black pepper to create the marinade.
Place the chicken breast, cubed sweet potatoes, and broccoli florets onto the prepared sheet pan.
Drizzle the lemon-herb marinade over the chicken and vegetables, tossing everything thoroughly to ensure an even coating.
Roast in the center of the oven for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the sweet potatoes are fork-tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep it juicy and tender.