I don't remember having to roast black walnuts.
I processed some once, years ago. My g'father, on Thanksgiving, took us out to a local HUGE black walnut tree and had us pick up a couple paper bags full of the nuts, in the husk.
Come Christmas, all the husks were black, so we dumped the nuts in the driveway, and walked over them to remove the husks. We picked the nuts off the ground, and would go at them with our nut-cracker, and a small nail to pick the nut meats out.
Peace, Love, and Vegetable Rights!
Eat Meat and Save the Plants!