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 1-inch bite-sized pieces and chop the broccoli, red bell pepper, and red onion into uniform chunks.
Place the chicken and all the vegetables onto the prepared baking sheet.
Drizzle the extra virgin olive oil over the chicken and vegetables, then sprinkle evenly with sea salt, black pepper, and garlic powder.
Toss everything thoroughly with your hands or tongs to ensure an even coating of oil and spices, then spread into a single layer.
Roast in the oven for 18 to 20 minutes, or until the chicken is fully cooked through and the vegetables are tender with slightly charred edges.
While the mixture roasts, ensure your brown rice is warmed through.
In a large serving bowl, combine the roasted chicken and vegetables with the warm brown rice.
Drizzle the tamari over the top and toss gently to incorporate all the flavors before serving.