Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch bite-sized pieces and slice the red bell pepper into thin strips.
In a large mixing bowl, combine the chicken, broccoli florets, and red bell peppers.
Drizzle the olive oil over the mixture and sprinkle with garlic powder, smoked paprika, sea salt, and black pepper.
Toss everything together until the chicken and vegetables are thoroughly and evenly coated with the oil and spices.
Spread the mixture in a single layer on the prepared sheet pan, ensuring there is space between the pieces so they roast rather than steam.
Place the pan in the oven and roast for 18 to 20 minutes, or until the chicken is cooked through and the broccoli edges are slightly charred.
While the chicken roasts, warm the pre-cooked brown rice in a small saucepan or microwave.
Divide the fluffy brown rice into a bowl and top with the roasted chicken and vegetable mixture.
Squeeze fresh lemon juice over the top before serving to brighten all the savory flavors.