Roasted chestnuts are a wonder yummy treat on a cold winter's night. I take mine and place them in a covered pot on the stove. I use no oil; but, you may add a drizzle if you like. I cook mine over a medium heat to avoid burning. At the beginning, shake the pan with medium enthusiasm. When the first chestnut pops in the pan, increase the shaking of the pan keeping the lid on the pan. After several chestnuts have popped, remove them from the pan and continue cooking the others. Keep removing them a few popped ones at a time.
A popped chestnut can be determined easily as there will be a split in the chestnut casing. When chestnuts are cooked (heated), the moisture in the chestnuts turns to steam. When the steam reaches the crisis point, the chestnut pops (not unlike the sound of popcorn) and indicates that the inside is cooked and good to eat.
I eat my chestnuts totally plain. I just peel the casing off and enjoy.