It's taken me years to get reliable crispy roasties but both my Dad and DH seem to think I've cracked it.
Yes, agree on the parboiling... I do big pieces with at least one straight edge, and time them 12 minutes from coming back to the boil, though check at 10 mins in case the spuds have started to fall. King Edwards are sods for this!
Yes on the shaking, yes on the letting steam escape and drying them off.
And definitely yes to a good tablespoon or two of goosefat! Baste when putting them in, and halfway through cooking (I do an hour at usual roast meat temp) I turn them and baste again. If still pale at the end, up goes the temperature to maximum and they get another 10 mins at the top of the oven.
DH gets the humph nowadays when we go somewhere and have soggy roasts. He had the humph himself on Sunday as I left him to do the parboiling and he didn't shake, and timed them from putting the boiled water on top of the spuds and not when they had come back to the boil. By the time I got back, they were halfway cold but with no rough surface, and wouldn't shake down, so they just didn't work.
Suspect I'll be back on duty next Sunday!