Preheat oven to 350°. In a greased 13x9-in. baking dish, layer half the potatoes; all the chilies, opened flat; all the salsa; half the sausage; and half the cheese. Cover with remaining potatoes, sausage and cheese.
Beat eggs and milk; add cumin, salt and pepper. Pour over potato mixture.
Bake, uncovered, until eggs are set in center, 35-40 minutes. Let stand 15 minutes. If desired, serve with warm tortillas, sour cream and additional salsa.