Baked is used mostly when referring to self made goods made from combining ingredients and putting them in the oven, usually using flour as one of the ingredients (e.g. cakes, bread, Biscuits). With 'bake', for example, you turn dough into cake, biscuits, etc. Roast is when you put a ready product (e.g meat, nuts, biltong) in the oven or direct heat to cook it through, but the product doesn't turn into something else e.g Raw chicken remains chicken, just roasted.