From the trees in my backyard (Chinese chestnut, not American). They taste like squash with the butter included, have a slightly rubbery texture since you're eating a glob of starch, and are profoundly fucking delicious. I haven't tried the imported ones I've seen in stores, though apparently they don't taste as good. I've seen those compared to potatoes.
To roast:
-Remove from husk
-Drop in a bucket of water, remove any that float
-Stick them on a baking sheet still wet and roast in the oven at 400F for 20 minutes
Some people put holes in them before roasting so they don't pop; I don't and haven't had any problems. A few might explode but that's less work peeling and no holes means they'll preserve longer.
To skin:
Cut off the tip of the pointy part with a knife/pair of scissors, then slit down the sides and peel away.
