Part boil the potatoes in salted water until two-thirds cooked. Drain and leave to cool.
Lightly dust the cooked potatoes with the flour so they are evenly coated.
Heat a roasting tin with the olive oil, add the potatoes, then place in the oven for approximately 45 minutes until tender.
Combine the crushed garlic, chopped rosemary, butter and lemon juice in a separate bowl.
Remove the tin from the oven, then add the garlic, rosemary and butter mixture. Gently fry for one minute until the potatoes are covered. Season with salt and pepper to taste.
Notes
You could substitute Rooster potatoes with other floury or all-purpose potatoes that are easily available. Varieties like Bintje or King Edward would make good alternatives as they have similar textural properties to Rooster potatoes.