While the potatoes are roasting, make your bean filling. Start by warming the oil in a medium saucepan. Saute the onion with a pinch of salt until softened, about 8-10 minutes. Add in the garlic, pepper, cumin, oregano, cinnamon, salt, allspice, and lime zest and cook for 1 minute, stirring. Add in the tomato paste and cook, stirring, for another minute, then pour in the chicken stock. Add the beans and bring to a low simmer. Taste for seasoning and add more salt if needed, and keep warm until the sweet potatoes are finished.