Par-boil the potatoes in gently boiling salted water for about 8 minutes. Stop cooking before they're cooked right through.
Leave to cool completely, then scratch roughly with a fork and season with a little fine salt.
Only roast around the joint if there is plenty of fat - at least ½cm/¾in in the tin - and plenty of room. It's better to preheat the oil in a separate pan, adding any beef fat from the roasting tin just before the potatoes go in. Don't add the potatoes until the oil is sizzling hot. Baste or turn the potatoes (carefully) as soon as they go into the pan so they have a light coating of oil from the start.
Roast for the last 45 minutes of your joint's cooking time, turning at least once. If they look like they could use a bit more browning/crisping, leave them in after the joint has come out to rest, while you increase the heat for the Yorkshire pudding.
Then, when the preheated pudding tin is ready you'll have to decide whether the potatoes come out, or stay in for the full 15 minutes of pudding time.
Drain well and keep in a warm oven, uncovered and not too piled on top of each other. Season again with salt and pepper before serving.