Cook the pasta according to the package directions. Spray the inside of the slow cooker with nonstick cooking spray. Turn the slow cooker on to low heat.
Layer half of all the ingredients, except the Daiya mozzarella-style shreds, in the slow cooker in the following order: spaghetti sauce, cooked rigatoni, ground Tofurky, and mushroom pieces. Repeat with the other half of each ingredient. Cook on low for 2 to 3 hours.
Sprinkle the Daiya mozzarella-style shreds over the top. Continue cooking on low for 30 to 45 minutes. Serve.