From the standpoint of method, there is no difference, since both techniques cook foods by dry heat in an oven. To a lexicographer or recipe writer, distinctions exists - and dish names such as "baked leg of lamb" or "roasted cake" would definitely raise culinary eyebrows. If the food you are cooking is a whole bird or a piece of meat that will later be divided for serving, then - in virtually all cases - you are roasting. With all other foods - hams, fish, single-serving portions of meat, casseroles, baked goods, including breads and cakes - you are, in popular terminology, baking.
Be prepared for a few established exceptions to the roasting versus nomenclature rule. For example, "baking" is not used to describe the fish dish "pan-roasted cod" because cod is browned in a skillet on a range before being finished in the oven.
** Asian Recipes