Preheat the oven to 400 degrees F (200 degrees C). Cover a large 12x17-inch baking sheet with aluminum foil and grease with cooking spray. Heat 1 tablespoon oil in a medium saucepan over medium-high heat. Add brown rice and saute for 2 to 3 minutes. Add water and salt. Cover and simmer over medium-low heat until water is absorbed, 20 to 30 minutes. Meanwhile, place sausages on one end of the baking sheet. Place onion next to the sausages. Place Brussels sprouts next to onion. Sprinkle garlic powder, salt, and pepper over vegetables. Drizzle with 1 1/2 tablespoons oil. Toss to coat. Roast in the preheated oven for 10 minutes. Remove baking sheet from the oven. Stir vegetables and turn sausages over. Add bell pepper to the baking sheet and drizzle with remaining 1/2 tablespoon olive oil. Season with salt and pepper. Toss to coat. Return to the oven for an additional 10 minutes. Let cool. Slice sausages into bite-sized pieces. Divide brown rice, vegetables, and sausage pieces evenly among the 5 containers. Top with Parmesan cheese.