Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Peel the sweet potato and cut into 1/2-inch cubes; core the apple and dice into similar sized pieces.
Trim the ends off the Brussels sprouts and slice them in half.
Cut the chicken breast into 1-inch bite-sized pieces to ensure even cooking with the vegetables.
Place the chicken, sweet potatoes, apples, and Brussels sprouts on the prepared baking sheet.
Drizzle with extra virgin olive oil and sprinkle with dried rosemary, sea salt, black pepper, and garlic powder.
Toss everything thoroughly with your hands or tongs until evenly coated, then spread into a single layer.
Roast for 20-25 minutes, tossing halfway through, until the chicken is cooked through and the sweet potatoes are tender and lightly browned.
Remove from the oven and let rest for 2 minutes before serving.