Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Prepare the ingredients by cutting the chicken breast into 1-inch cubes, dicing the sweet potato into similar sizes, slicing the carrots into rounds, and halving the Brussels sprouts.
Place the chicken cubes and all the prepared vegetables into a large mixing bowl.
Drizzle the extra virgin olive oil over the mixture and sprinkle with sea salt, black pepper, garlic powder, and dried rosemary.
Toss everything together thoroughly using your hands or large spoons until the chicken and vegetables are evenly coated in oil and spices.
Spread the mixture in a single, even layer across the prepared baking sheet, ensuring the pieces aren't too crowded so they roast rather than steam.
Roast in the center of the oven for 20 to 25 minutes, tossing the ingredients halfway through, until the chicken is cooked through and the vegetables are tender with golden-brown edges.