Preheat the oven to 425 degrees. Drizzle the oil in a cookie sheet. Heat the cookie sheet for 5 minutes. Place the Brussels Sprouts evenly on the cookie sheet. Bake 5 minutes. Add the green beans, rice, and onions to the pan. Bake another 10 minutes or until heated through. When finished transfer to a serving dish. Squeeze the lemon juice over the serving dish. Sprinkle with salt and pepper to taste.