In a medium bowl, mix together the ricotta and egg whites.
Grease the inside of a slow cooker with nonstick spray. Pour 2 cups (460 G) of Prego® Traditional Italian Sauce into the bottom of the slow cooker, then layer half of the pasta, half of the meatballs, half of the ricotta mixture, and 1 cup (100 G) of mozzarella on top. Repeat to make another layer, then dollop the remaining ½ cup (115 G) tomato sauce on top and sprinkle with the remaining ½ cup (50 G) mozzarella.
Cover the slow cooker and cook on high for 3 hours (or low for 6 hours),or until the meatballs are warmed through and the pasta is tender.