Spray 4- to 6-quart slow cooker with cooking spray. Halve larger sweet potatoes lengthwise; cut each into 1/2-inch slices. Place in slow cooker. Add pie filling, 2 tablespoons margarine, the gingerroot and salt; mix well to coat potatoes.
Cover; cook on High setting 2 1/2 to 3 1/2 hours.
Meanwhile, line cookie sheet with foil. In small skillet, combine all Topping ingredients. Cook over medium heat 2 to 3 minutes, stirring frequently, until bubbly and glazed. Spoon onto foil-lined cookie sheet to cool.
Just before serving, gently stir potatoes. Sprinkle with topping.