Preheat the oven to 375. Wash sweet potatoes and prick them with a fork. Place the sweet potatoes in a sheet pan covered with tin foil (for easy clean up).
Roast the sweet potatoes in the oven for 1.5 hours until they caramelize and ooze with liquid.
Add all the remaining ingredients in another bowl and mix together.
Let the sweet potatoes cool slightly and peel them. Place the sweet potatoes in a mixing bowl and mix to puree.
Place your combined ingredients with your sweet potatoes and mix to combine. Pour this mixture in a greased 9X9 pan.
Reduce oven temperature to 350. Bake the sweet potatoes for about 30 minutes. Proceed with the marshmallow topping if desired.