You can actually use your gas grill but if you have access to a propane roaster you have a much easier way to roast a lot of chile in a short time. With any green chile (even poblano) you want to char the crap out of the outside skin. You want the chile to be a wilted shriveled up blackened limp thing when you pull it off the fire or roaster. Then put the chile in a plastic bag and seal it so that the steam and heat sweats the skin which will make it peel off easier. Let it sweat for about 30-60 min or so.
You need to peel off the outer skin which leaves a nice tender chile (whole) and you are ready to go. You can freeze the chile in a freezer bag and then thaw what you need and refreeze. Chop the chile up just before you use it then add into your dish or pizza or burger etc.
Aside from the green chile cheese burger which is to die for good one of the best uses is on pizza! A "Roadrunner" Pizza is Italian Sausage and green chile.
Just an amazingly wonderful combination. The green chile breakfast burritos are a staple around here. Scrambled eggs, hash browns, sausage (or bacon), green chile, cheese all wrapped up in a flour tortilla.
This time of year I like to make an Iron Skillet Breakfast Casserole. Its so easy and so good plus you cook and bake in the same pan.
I use a whole pound of Owen's (or Jimmy Dean) tube sausage, 4 cups of hash browns, 1 cup chopped onion, 1 cup of HOT chopped Hatch green chile, about 10 eggs depending on their size and about 1.5 cups of cheese on top.
Cook the sausage first, then add the onions, then add the hash browns into the pan, green chile, stir up well cook hash browns for a few minutes to brown, pat flat, pour the egg mixture (plus S&P and a little milk to help them fluff up) on top, sprinkle the cheese on top and bake for 40 mins at 350.
Bon appetit!