Because of the size of chestnuts and the temperature difference of each oven, the baking time provided in the formula is for reference only. When the roast is almost done, you can take out a chestnut and taste it to see if it is ripe. If not, extend the baking time. Chestnuts must be completely roasted to be delicious.
Cutting a hole in chestnuts with a knife can make chestnuts crack smoothly during baking. If you are lazy and omit this step, you should be prepared that the oven will make a loud noise when chestnuts are roasted. Not all chestnuts can crack.