In a large deep skillet (or pot), brown the italian sausage.
Melt the butter in the pan and sprinkle in the red pepper flakes. Cook for 1-2 minutes, then deglaze the pan with the vodka. Simmer for 4-5 minutes to cook off the alcohol.
Pour in the tomato sauce, diced tomatoes, milk, cream and water; stir to combine. Add in the pasta, stir again, cover (but vent!), reduce heat to medium low and simmer for about 10 minutes.
Uncover the pasta and stir in the frozen shrimp. Re-cover and simmer for another 5 minutes.
Add in the parmesan cheese and mix until melted. Add more milk and cream if more sauce is needed.