Preheat oven to 350°.
Bake potatoes at 350° for 1 hour or until tender. Let cool; peel and cut into chunks. Place potatoes and bananas in a food processor; process until smooth. Add melted margarine, 2 tablespoons sugar, nutmeg, cinnamon, and salt; pulse until blended. Divide sweet potato mixture evenly among 6 (8-ounce) ramekins.
Melt 1 tablespoon margarine in a small saucepan over medium-high heat. Add 2 tablespoons sugar; cook 1 minute. Add pecans; cook 1 minute, stirring constantly. Remove from heat; divide pecan mixture evenly among ramekins. Bake at 350° for 25 minutes or until thoroughly heated.