To make this Slow Cooker Sweet Potato Casserole, start by spraying your slow cooker with non-stick spray. Next, drain your canned sweet potatoes, add to the slow cooker and using a fork or a potato masher, lightly break up the sweet potatoes and mash them to your desired consistency.
Next, add in the sugar, vanilla, butter and brown sugar along with the orange juice, eggs, milk and spices and using a hand mixer, beat together to combine.
Smooth mixture out evenly and in a small bowl, combine brown sugar, flour, melted butter and pecans. Sprinkle evenly over the sweet potatoes. Cover and cook on High for 3 - 4 hours.
Right before serving, top with mini marshmallows, cover and let marshmallows melt. Reduce your heat to Warm and serve your Slow Cooker Sweet Potato Casserole directly out of the slow cooker.