Cook sausage thoroughly over medium heat. Drain and set aside.

In a small bowl, stir together ricotta cheese, egg, basil and, if desired, red pepper flakes.

Pour pasta sauce into a 5-qt. slow cooker. Stir in cooked sausage. Top with pasta and pour water over top.

Drop ricotta cheese mixture by heaping tablespoonfuls over pasta. Sprinkle with mozzarella cheese.

Cook, covered, on high until heated through and pasta is tender, 2 to 2-1/2 hours. Top with Parmesan cheese.