Preheat the oven to 375°. In a large skillet, heat the olive oil. Add the sweet potatoes and cook, stirring occasionally, until browned, about 10 minutes. Add the scallions, garlic and pimentón and cook for 1 minute. Season the hash with salt and pepper and transfer to an 8-inch square baking dish. Bake the hash for 10 minutes, or until the potatoes are tender.