Preheat oven to 350 degrees. Carefully mix the shrimp, crabmeat, 1/2 jar of Alfredo sauce, 1/2 of the cheese and a sprinkle of Old Bay seasoning in a large mixing bowl. Divide the mixture evenly amongst the tortillas. Roll each tortilla and place seam side down in a greased 9x13 baking dish. Evenly pour the remaining Alfredo sauce on top. Cover with the remaining cheese. Bake for 30 minutes or until the cheese is hot and bubbly.