Sausage Potato Breakfast Casserole

Italian sausage ((spicy or mild))

onion (chopped)

white mushrooms (chopped)

green bell pepper (chopped)

red bell pepper (chopped)

eggs

milk ((I used 2%))

salt

black pepper

red pepper flakes

frozen hash brown potatoes (cubed (1 bag))

mozzarella cheese (shredded)

green onions (chopped)