First, preheat the oven to 375F then remove the frozen burritos from the package and arrange them in the baking dish.
Next, in a bowl combine the sauce, salsa and tomato sauce together. Now, pour that right across the top of the frozen burritos.
Then, place in preheated oven for 30 minutes. At the 30 minute mark remove the baking dish and top with cheese. Place the casserole back in and bake a remaining 25 minutes.
Lastly, allow the frozen burrito casserole to cool a bit before serving.