Preheat the oven to 400°F and wash the potatoes. Place them on a foil lined baking sheet and bake for about an hour or until they are soft and knife easily slides through the middle of each potato. Allow to cool enough to handle.
In a small bowl, stir together the brown sugar, pecans, and cinnamon. Set aside.
When the potatoes are cool enough to handle, cut a slit down the potato and carefully scoop out the flesh. In a medium bowl, combine the sweet potato flesh with the butter, cream cheese, salt, and about 2/3 of the brown sugar mixture. Mix well to combine. Carefully spoon the mixture back into the potatoes. Sprinkle the top with the remaining 1/3 of the brown sugar mixture and place back on the baking sheet. Bake for an additional 15 minutes.
Remove from the oven and top with the marshmallows, bake for an additional 5 minutes or until the marshmallows are golden brown. Serve warm.