Choose Hatch chiles that are a glossy, bright green. They should be firm and heavy for their size. For easy roasting, pick out relatively straight or flat peppers because they will turn more easily and blacken evenly.
There are several methods for roasting, but for each method use tongs to turn the peppers until the skin blackens and blisters evenly.
On the grill, place chiles about 5 inches above a gas or charcoal fire.
If you have a gas stove, you can position the chiles on a stove top grill over high heat. If you have an electric stove, use a cast-iron skillet. Place the skillet on a burner over high heat.
You can also broil the peppers. Position chiles on a baking pan and set under the broiler for 6 to 8 minutes, or until skin blisters.
After roasting, place chiles in a sturdy plastic bag and close. In about 10 minutes, the steam will soften the skin so that it peels off more easily, using your hands or a knife. Don't rinse the chiles under water because it will remove flavor.
Peeled, roasted chiles can be frozen in plastic bags. And while I can't imagine them not being eaten sooner, frozen chiles will keep up to two years.