Roast the potatoes. Line a cookie sheet with tin foil and bake at 425º F for 50-60 minutes. When done the skin and flesh should be easily pierced with a fork.
Let the potatoes cool for 15 minutes, then cut in half and scoop out the potatoes into a large bowl. You want the potatoes hot when you the casserole so all the ingredients blend well together.
Lower oven temperature to 350ºF.
In a medium bowl, mix the ricotta cheese, butter, brown sugar, eggs, vanilla, and spices. Mix well.
Add the ricotta mixture to the potatoes. Mix until all the ingredients are completely combined.
Pour into a 7x11 inch casserole dish.
Make the crumble topping by mixing all the ingredients in a small bowl.
Sprinkle over the top of the potato mixture.
Bake 30 minutes.
Let cool 20 minutes.
Spread marshmallow cream over the top of the casserole, leaving a 1 inch border all the way around. The marshmallow cream will spread as it bakes.
Sprinkle surface of marshmallow cream with mini marshmallows.
Bake at 350º F for 5 minutes or until marshmallows are browned. Keep a very close eye on the marshmallows as browning can happen very quickly.
Serve warm.