Preheat the oven to 400 degrees Fahrenheit and prepare a baking sheet by lining it with parchment paper.

In a bowl, add the cubed sweet potatoes along with the olive oil, cinnamon, and nutmeg, gently mixing until the sweet potatoes are fully coated.

Add the sweet potatoes to the baking sheet in a single layer and bake for 50-60 minutes or until tender, charred, and golden. Remove from oven and let cool slightly.

Preheat the oven to 375 degrees Fahrenheit and lightly grease a large 9x13 baking dish.

In a bowl, add the roasted sweet potatoes, milk, vanilla, brown sugar, maple syrup, cinnamon, nutmeg, allspice, raisins, and marshmallows, mixing until combined. It’s okay if some sweet potato starts to mash; you want a mixture of mashed and chunks.

Scoop the mixture into the prepared baking dish, spreading it evenly. Add pieces of butter throughout the casserole mixture and tuck in a few additional marshmallows if desired.

In a bowl, add the pecans and maple syrup, stirring until combined.

Generously add the topping over the sweet potato casserole mixture until fully covered. Cover with foil paper.

Bake with foil for approximately 15 minutes, then remove the foil and finish baking for the remaining 15 minutes or until the top is golden brown and the marshmallows have melted.

Remove from the oven and let cool slightly before serving.