Roast potatoes are simple to describe but surprisingly easy to get wrong. Some are pale and soft, others burn at the corners before the centre becomes tender, and a few seem to stick so firmly to the tray that the crispest part gets left behind.
The most reliable method is to start with suitable floury potatoes, parboil them, allow moisture to escape and put them into properly heated fat with space around each piece. Good Food's roast-potato recipes differ in exact oven temperatures and timings, but those stages appear repeatedly.
Pick a potato for roasting
Maris Piper and King Edward are popular choices because their interiors become floury when cooked. Désirée can also give good results.
A very waxy potato may hold its shape well but have a firmer centre and less fluffy exterior. That can still be enjoyable, but it's a different style of roast.
Use sound potatoes, trimming limited damage and discarding any with substantial greening, rot or an unpleasant smell.
Choose pieces of roughly similar size. A tray containing tiny cubes and fist-sized halves won't roast evenly.
Peel or leave the skin on?
Peeled potatoes produce a wide surface that can roughen during parboiling. That makes it easier to develop a thick browned crust later.
Skin-on roast potatoes have their own appeal, especially small new potatoes. They often develop a thinner crisp skin and a different texture.
For a classic fluffy Sunday roast, peel the potatoes, then cut larger ones into halves or quarters.
Wash them before cooking so loose starch and dirt don't remain on the outside of the prepared pieces.
Parboil before roasting
Put the potatoes into a large pan with cold water and a little salt. Bring to a boil, then reduce the heat to a gentle simmer.
Cook until the outer surface has softened enough to roughen but the pieces can still be lifted without collapsing. The exact timing depends on the size and variety.
Some Good Food methods use a very short parboil followed by extended roasting; others cook the potatoes until tender before drying and roasting. Follow one coherent recipe rather than combining timings blindly.
Drain carefully and allow the hot potatoes to sit briefly so steam can escape.
Roughen the surfaces carefully
Return the drained potatoes to the pan or leave them in a colander. Shake gently to scuff the soft outer edges.
Those roughened bits can become wonderfully crisp in hot oil. Don't keep shaking until all the pieces break into crumbs.
Some recipes dust the potatoes lightly with plain flour or semolina to increase the crust. If you use that approach, follow the recipe's quantity rather than pouring in a thick coating.
Letting the potatoes steam-dry after boiling helps the surface brown instead of steaming in the oven.
Choose oil or roasting fat
Vegetable, rapeseed and suitable olive oils can make good roast potatoes. Goose fat and duck fat add a different flavour but aren't essential.
Choose a fat appropriate to the oven temperature you're using. Heat it in a sturdy roasting tray as instructed by your recipe.
Be careful when adding damp potatoes to hot fat, because it can spit. Lower pieces into the tray with suitable utensils rather than dropping them from a height.
You need enough fat to coat the outside, not so much that the potatoes are swimming in a dangerous deep layer.
Give the potatoes room
Arrange the pieces in one layer. They should have gaps around them rather than being stacked.
When a roasting tin is overcrowded, moisture becomes trapped and the potatoes are more likely to steam instead of brown.
Use two trays if you're making a large family meal. Be prepared to rotate them if your oven has noticeably uneven heat.
A high-sided roasting tin reduces the likelihood of hot fat spilling as you turn the potatoes, but avoid making the tray so deep and crowded that steam cannot escape.
What oven temperature should you use?
Good Food has roast-potato recipes using settings such as 190°C conventional / 170°C fan and others at 200°C conventional / 180°C fan.
The best setting depends on the cut size, preparation method, fat and oven. Choose a specific recipe and follow its heat and timing together.
Preheat the oven thoroughly, along with the roasting fat where instructed. Putting wet, cool potatoes onto a cold tray often delays browning.
If the edges darken too quickly while the centres remain firm, lower the heat a little and continue cooking rather than allowing them to burn.
When to turn roast potatoes
Leave the potatoes undisturbed long enough for the underside to develop a browned crust, then turn them with a spatula.
Many roast-potato recipes turn the pieces at intervals of fifteen to twenty minutes. A very short total cooking time isn't suitable for huge chunks.
If a potato sticks, try loosening it gently after a little more roasting time. Pulling it off forcefully can leave the crust behind.
Rotate trays in the oven if one area is consistently much hotter than another. You don't need to turn every piece constantly.
How do you know when they're ready?
The outside should have plenty of golden colour and feel crisp when lightly pressed with a spatula. The middle should be tender and fluffy when you break one open.
A large piece with dark edges but a firm centre needs more cooking. Lower the heat slightly if it is becoming over-browned.
Taste one, allowing it to cool enough not to burn your mouth. A little extra salt is easier to add after cooking than to remove from a heavily salted tray.
Serve as soon as practical. Potatoes piled into a deep covered bowl release steam that can soften the crust.
Freezing roast potatoes in advance
Good Food suggests parboiling, roughening and tray-freezing prepared pieces before the final roast. This lets you move straight from freezer to oven when needed.
Cool the potatoes promptly, spread them separately on a tray and freeze until hard. Then transfer to labelled freezer bags.
Cook from frozen using a suitable roast-potato recipe, giving enough time for the centres to become thoroughly hot and the outsides browned.
A large bag that was frozen while the pieces were still wet may be difficult to separate and can steam when roasted.
What if the potatoes aren't crisp?
Check the variety first. Very waxy potatoes may produce a different texture from a floury variety.
Next consider the parboil and drying. If the surfaces weren't softened and roughed up, they have less potential for crisp edges.
An overcrowded tray is another common problem. Give the pieces space and use a hot oven with suitable fat.
Finally, check whether the potatoes stood covered for too long after cooking. A wonderful crust can soften quickly when steam is trapped.
Leftovers and reheating
After dinner, move the extra roast potatoes into a shallow container to cool quickly before refrigerating. Eat refrigerated leftovers within two days or freeze suitable portions, following Food Standards Agency advice.
An oven or air fryer may restore some of the exterior crispness when reheating. Whatever appliance you choose, ensure the centres are thoroughly hot.
Don't repeatedly reheat the entire leftover batch. Separate a portion and leave the rest appropriately chilled.
For a reliable Sunday roast, concentrate on the preparation: even pieces, a short careful parboil, dry roughened surfaces, enough tray space and proper heat.
Sources checked
Good Food: how to make roast potatoes and Good Food: roast potato recipes.