Whether you get your chiles from the local supermarket or pick them fresh in the fields, select large, firm, meaty chiles with no sign of wilting. Wash the chiles before proceeding.
Slit each pepper lengthwise, and scrape out the seeds and membranes with a spoon. Some people don't remove the seeds before roasting, but we think they're easier to remove at this stage if you plan to freeze them for later use. Also, we think freezing peppers with the seeds and membranes inside makes them hotter when thawed and used later. By the way, when handling chiles, either wear gloves or coat your hands with vegetable oil, and don't touch eyes or other sensitive areas.
If roasting the chiles indoors, arrange them in a single layer on a baking sheet. A layer of foil makes for easier cleanup later.
Place in the oven, 4-5 inches from the the broiler element. The skin will blister and turn black. Turn the peppers as required to blister all sides evenly. At this point, your kitchen should be filled with the mouth-watering aroma of roasting green chile!
If it's a nice day outdoors, and if you have a good gas barbecue grill, you can roast your chiles that way. Arrange the peppers over high heat, turning as necessary to blister the skins evenly on all sides.
Whichever roasting method is used, the pepper skins should be evenly blistered, mostly black. Cover the hot chiles with a damp kitchen towel for 15 minutes or so. This steams them and loosens the skins. You can also use a plastic or paper bag to steam the peppers.