Preheat the oven to 375 degrees. Brush a rimmed baking sheet with olive oil. In a large bowl, toss the potatoes, peppers and 1 tbsp. oil; season with salt and pepper. Spread in a single layer on the baking sheet. Roast until tender, about 25 minutes.
Meanwhile, in a large pot, heat the remaining 3 tbsp. oil over medium. Add the onion; season. Cook, stirring often, until the onion is soft, about 5 minutes. Stir in the garlic and spices. Cook until the spices are fragrant, about 1 minute.
Add the chicken. Cook, stirring often, until the chicken browns, about 5 minutes. Stir in the beans, tomatoes, stock and cocoa. Bring to a gentle simmer. Cook, stirring occasionally, until the chicken is tender, about 45 minutes; season.
Add the roasted vegetables to the pot. Cook, stirring occasionally, until the flavors meld, about 15 minutes. Divide the chili among bowls; top with the cilantro. Serve with the toppings, if using.