Preheat the oven to 400F. Place the chicken thighs, sausage, peppers, celery, and jalapeno on a large (11x17 inches or larger) rimmed sheet pan. Toss to combine.
Drizzle with half of the melted butter and sprinkle with half of the Cajun seasoning. Toss again to combine well. Bake 12 minutes.
Remove from the oven and top with the cauliflower rice, tomatoes, and shrimp. Drizzle with the remaining butter and Cajun seasoning - no need to toss together at this point.
Bake another 10 minutes, then turn on the broiler and broil 2 to 4 minutes. Remove from the oven, toss to combine all of ingredients, and serve hot.