Preheat your oven to 400°F (200°C) and line a large rimmed sheet pan with parchment paper for easy cleanup.
Peel the sweet potato and cut it into 1/2-inch cubes, and slice the chicken breast into bite-sized pieces.
Place the chicken pieces, sweet potato cubes, and broccoli florets onto the prepared sheet pan.
In a small glass jar or bowl, whisk together the olive oil, lemon juice, lemon zest, oregano, garlic powder, sea salt, and black pepper.
Pour the lemon-herb dressing over the chicken and vegetables, tossing thoroughly with your hands or tongs to ensure every piece is well-coated.
Spread the mixture into a single, even layer on the pan to ensure proper roasting.
Bake for 20 to 25 minutes, or until the chicken is cooked through and the sweet potatoes are fork-tender and slightly caramelized.