1. Preheat oven to 400°. Bake sweet potatoes on an aluminum foil-lined 15- x 10-inch jelly-roll pan 1 hour or until tender. Reduce oven temperature to 350°. Cool potatoes 30 minutes.
2. Meanwhile, cook carrots in boiling water to cover 20 to 25 minutes or until very tender; drain.
3. Process carrots and butter in a food processor until smooth, stopping to scrape down sides as needed. Transfer carrot mixture to a large bowl.
4. Peel and cube sweet potatoes. Process, in batches, in food processor until smooth, stopping to scrape down sides as needed. Add sweet potatoes to carrot mixture. Stir in sour cream and next 5 ingredients, stirring until blended. Spoon mixture into a lightly greased 13- x 9-inch baking dish.
5. Bake at 350° for 30 minutes or until thoroughly heated. Remove from oven. Sprinkle with marshmallows. Bake 10 more minutes or until marshmallows are golden brown. Remove from oven, and sprinkle with Sugar-and-Spice Pecans.
Note: To make ahead, prepare recipe as directed through Step 4; cover and chill up to 24 hours. Remove from refrigerator, and let stand 30 minutes. Proceed with recipe as directed in Step 5.