Preheat oven to 350F and grease a 9x13 casserole dish. Cook ziti in salted pasta water - cook 2 minutes less than package instructions.
Cut casing off of the sausage and cook and crumble in a skillet over medium heat until cooked through, about 5-7 minutes. Allow sausage to cool slightly.
Mix the marinara sauce, ricotta cheese, Italian seasoning and salt in the casserole dish. Mix in the cooked sausage and then the cooked and drained ziti pasta. Mix until everything is evenly combined. Top with the mozzarella cheese.
Cover with foil and bake in the oven at 350F for 30 minutes. Uncover and broil for just a couple minutes to brown the cheese.
Notes
Freezer Instructions: Do not bake after assembly. Allow the casserole to cool completely. Cover with 2 layers of tinfoil and freeze for up to 3 months.
Reheat After thawing: Bake covered at 350F for 45 minutes. Uncover and bake a bit longer to brown the cheese.
Reheat From frozen: Bake covered at 350F for 2 - 2 and a half hours.Uncover and bake a bit longer to brown the cheese