My brother says he has eaten one which he lightly roasted and it was slightly bitter.

I love bay nuts! For most people they have a very caffeine-like effect, so be careful when eating more than a few.

They should be gathered in the fall when they fall off the tree. If you look for trees on a hillside you can often go to the bottom and scoop the rollers!
Husk them- inside there's a hard-shelled tan nut. If the husks are all moldy, you should have gone sooner. They should be a greenish-yellow, sometimes purplish, and firm to slightly wrinkled. The husks will turn your fingers orange for a few days if you do enough of them, so maybe they could be used for a dye? I've also heard that people eat them fresh, but I never had.
Once you have some nuts, let them dry for a few days or a week, then roast them. The sites I've read and other people I've talked to roast them briefly at high temps, but sometimes when I do this they explode. Instead I put them in the oven at about 2-300 until when cracked they're dark brown. Dark like coffee beans, not just brown. Often the shells will crack when they're done, but sometimes at low temps this doesn't happen, so check regularly. If you roast them well, the bitterness should fade, leaving a coffee/chocolate type flavor. The nuts are easy to crack with your teeth for the meat inside, or use a rock. They're really great in the mornings if you're like me and can't handle coffee.

Some people like them, some don't. For the record though, everyone that I've talked to that didn't like them had a different way to prepare them.