Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Peel and cube the sweet potato into half-inch pieces, and slice the zucchini into half-moons.
Place the chicken breast, cubed sweet potato, broccoli florets, and zucchini onto the prepared baking sheet.
Drizzle the olive oil and lemon juice over the chicken and vegetables.
Evenly sprinkle the dried oregano, sea salt, black pepper, and garlic powder over everything.
Toss the vegetables and chicken thoroughly with your hands or tongs to ensure every piece is well-coated in the oil and seasonings.
Spread the ingredients out into a single layer, ensuring the chicken has space around it to roast properly.
Roast in the oven for 20 to 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.