Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into uniform 1-inch cubes and place them in a large mixing bowl with the broccoli florets.
In a small jar or bowl, whisk together the orange juice, tamari, honey, sesame oil, arrowroot powder, garlic powder, ginger, sea salt, and black pepper until the starch is fully dissolved.
Pour the orange glaze over the chicken and broccoli, tossing thoroughly to ensure every piece is well-coated.
Spread the mixture in a single layer on the prepared baking sheet, ensuring the pieces are not overcrowded so they roast rather than steam.
Bake for 18 to 20 minutes, or until the chicken is cooked through and the sauce has thickened into a sticky glaze.
Serve the orange chicken and broccoli over the warm cooked brown rice and garnish with a sprinkle of sesame seeds.