Add the goose fat to the cast iron skillet and heat it in the oven for 5 minutes, just enough to melt the goose fat.
Add the potatoes to the skilled and stir them to coat them with the melted goose fat.
Sprinkle your BBQ rub mixture over the potatoes and give them a stir.
Roast the potatoes in a 425 °F oven. Flip the potatoes after 20 minutes, then cook an additional 25 minutes (for a total of 45 minutes) until golden brown on the outside.