Heat oven to 350°F. Cook and drain pasta as directed on package. Rinse with cool water; drain.
Meanwhile, in 10-inch nonstick skillet, cook sausage over medium-high heat 5 to 7 minutes, stirring occasionally, until no longer pink; drain. Stir ricotta cheese and egg into sausage.
In medium bowl, mix tomato sauce, Italian seasoning and garlic powder. In 13x9-inch (3-quart) glass baking dish, spoon 1 cup tomato sauce mixture over bottom. Spoon about 2 tablespoons sausage mixture into each pasta shell. Arrange shells on sauce in baking dish. Spoon remaining sauce over stuffed shells.
Bake uncovered 30 minutes. Sprinkle with cheese. Bake uncovered about 10 minutes longer or until cheese is melted.