Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Cut the chicken breast into 1-inch bite-sized pieces and place them in a bowl with avocado oil, sea salt, and black pepper, tossing to coat.
Spread the chicken in a single layer on one half of the prepared baking sheet and roast for 10 minutes.
While the chicken starts roasting, whisk together the orange juice, tamari, honey, grated ginger, minced garlic, and arrowroot powder in a small saucepan over medium heat.
Simmer the sauce for 3-5 minutes until it thickens into a glossy glaze, then remove from heat.
Add the broccoli florets to the other side of the baking sheet and roast everything for an additional 10-12 minutes until the chicken is cooked through and broccoli is tender.
Transfer the roasted chicken and broccoli to a large bowl, pour the orange glaze over them, and toss until every piece is thoroughly coated.
Serve the orange chicken and broccoli over the warm cooked brown rice and garnish with sesame seeds.