Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel the sweet potato and dice into small 1/2-inch cubes to ensure they cook at the same rate as the chicken.
Cut the chicken breast into 1-inch bite-sized pieces and chop the broccoli into bite-sized florets.
In a large mixing bowl, combine the chicken, sweet potato, broccoli, and sliced red bell pepper.
Mince the garlic and whisk it together with the olive oil, lemon juice, dried oregano, sea salt, and black pepper in a small jar.
Pour the lemon-herb dressing over the chicken and vegetables, tossing thoroughly to ensure everything is well-coated.
Spread the mixture onto the prepared baking sheet in a single even layer, avoiding overcrowding.
Roast for 20 to 25 minutes, or until the chicken is cooked through and the sweet potatoes are tender with slightly caramelized edges.
Remove from the oven and serve immediately, optionally garnished with fresh parsley or an extra squeeze of lemon.