I tried my hand at "proper" crispy roast potatoes at the weekend and they turned out brilliantly, so I will document the recipe I used here.
* I used 'King Edwards' potatoes.
Turn the oven to 200 Celsius/400 Fahrenheit/Gas Mark 6 and allow to heat up while you prepare.
Cut the potatoes into decent sized chunks.
Bring a large sauce pan of salted water to the boil.
Add the potatoes and boil for about 6 minutes, until they can be easily "fluffed" with a fork.
While they are boiling, add the oil/rosemary to a roasting dish and place in the oven to heat up.
Once they are boiled, drain and put them back into the saucepan.
Mix the flour/turmeric together, with some salt/pepper to taste and sprinkle over the potatoes.
Place the lid back on the saucepan and shake vigorously until the potatoes are coated/fluffy.
Remove the dish from the oven and add the potatoes to it.
Roast the potatoes for about 40 minutes.