Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Dice the chicken breast into 1-inch cubes and place them in a large mixing bowl.
Peel and chop the sweet potato and carrots into 1/2-inch pieces, and halve the Brussels sprouts, adding them to the bowl with the chicken.
Drizzle the olive oil over the chicken and vegetables, then sprinkle with sea salt, black pepper, garlic powder, and dried thyme.
Toss everything thoroughly until the ingredients are evenly coated in the oil and spices.
Spread the mixture in a single layer on the prepared baking sheet, ensuring enough space for the vegetables to roast rather than steam.
Roast for 25-30 minutes, tossing halfway through, until the chicken is cooked through and the vegetables are tender with golden, caramelized edges.
Remove from the oven and serve immediately while warm.