Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch bite-sized pieces and place them in a large mixing bowl.
Halve the Brussels sprouts and the baby potatoes, then add them to the bowl with the chicken pieces.
Drizzle the olive oil over the mixture and sprinkle with garlic powder, onion powder, dried thyme, sea salt, and black pepper.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the oil and seasonings.
Spread the mixture in a single layer on the prepared baking sheet, ensuring space between pieces to allow for even browning.
Roast for 20-25 minutes, tossing halfway through, until the chicken is cooked through and the potatoes are fork-tender with charred edges.
Remove from the oven and drizzle with fresh lemon juice before serving to brighten the flavors.