Char the bell pepper under the broiler or over an open flame until blackened all over. Transfer to a bowl, cover and let cool, then peel, seed and chop.
In a dutch oven, heat the EVOO, 1 turn of the pan, over high heat until smoking. Add the lamb and brown well. Add the carrot, onion, garlic and rosemary; season liberally with salt and pepper. Stir in the cloves, bay leaf and orange zest. Once the onion has softened, add the tomato paste and stir until fragrant, 1 minute or so. Stir in the wine to deglaze the pot. Add the stock, milk, olives and bell pepper. Lower the heat and simmer.
Meanwhile, bring a large pot of water to a boil, salt it, add the pasta and cook until al dente. Drain, reserving a cup of the pasta cooking water. Remove the bay leaf from the sauce, then toss the pasta with the sauce, adding enough of the pasta cooking water to coat the pasta evenly. Serve the pasta in shallow bowls with the pecorino-romano and chopped nuts.