Preheat oven to 425 degrees F.
Cook the potatoes in salted boiling water for about 15 minutes, or until your knife slides easily through them. Drain and leave for 5 minutes.
Drizzle a roasting tray with a little olive oil and any handy pork fat. Season, then throw in the potatoes, and push down on each of them to break them up slightly. Then pound up the rosemary in a pestle and mortar to bruise and release its flavors. Add 4 good lugs of olive oil, stir around, and drizzle over the potatoes. Roast for 40 to 50 minutes at 425 degrees F (220 degrees C/gas 7) until crisp and golden.