I never bother with roast potatoes - but I do make Yorkshire puddings for the meals we have with our daughter.
I use three eggs, salt, then cream and water or milk with butter, and 2 cups of white bread flour when I can get it otherwise ordinary plain flour.
I use 8 muffin tins to cook them which I heat up with fat from roasted meat - usually lamb. I turn the thermostat up to the top to get the oven and the fat really hot, pour in the batter and close the door gently. I turn down the heat a little, but the numbers came off the metal long ago so I can't tell you the temperature.
My American son in law eats them with butter and cheese, rather than with gravy, but we all seem to cope with that.