In a large stockpot, combine the roasted bones and vegetables, the pan juices, parsley, bay leaf, peppercorns, and garlic and season with salt. Add enough cold water to just barely cover and bring to a boil over high heat. Turn the heat to low and simmer, uncovered, for 45 minutes. Partially cover the pot and simmer for another 1 to 3 hours (see headnote), or until the stock has a rich, full flavor. Taste and adjust the seasoning, adding more salt and ground pepper if needed.