Agreed it gives roasties a lovely crispy skin but the key to good roasties in my opinion is to first of all have a good spud (personally I like a rooster for this) and secondly to parboil the potatoe first before roasting to ensure the inside is nice and soft.
after parboiling them, give them a little shake in a covered saucepan to "fluff" them up a bit. Then toss them in the hot goose fat which will crisp up the fluff and give fab roasties