Pumpkin Pie Spiced Pork Loin with Sweet Potato Casserole

Name: Pumpkin Pie Spiced Pork Loin with Sweet Potato Casserole
Ingredients: 1 cup packed light brown sugar; 2 teaspoons pumpkin pie spice; 1/2 teaspoon garlic powder; 1/2 teaspoon onion powder; 1/2 teaspoon mustard powder; Kosher salt and freshly ground black pepper; 2 tablespoons olive oil; One 4-pound boneless pork loin roast; 2 tablespoons unsalted butter, plus more for the baking dish; 2/3 cup packed light brown sugar; Kosher salt; 2 1/2 pounds sweet potatoes (about 5); 1 lemon, sliced and seeded; 1/2 cup chopped pecans; 3 cups marshmallows