Are you in for a treat!!!
When I first did this last year, I felt like I'd discovered a new
planet, I loved them so much (still do). I prefer the red or yellow for
roasting .. the green have skin so thin that the "meat" burns so easily
it's a pain to me.
You can use any heat source, really .... gas or flat top burner (not
willing to juice up my electric range but you can), hot skillet (some chefs
use oil .. ick) or griddle, or a broiler.
I use the broiler and a cookie sheet with a lip covered with foil (with
edges turned up to catch the juices .. they're good and I hate to clean
unnecessarily). On the highest rack (or your preferred heat source, really
doesn't matter), let them blister until black, watching and turning so ALL
sides, top and bottom, are black (<-- this is key, not just mottled and
slightly blistered). This takes about 20-25 minutes altogether, as I
recall, but watch carefully and be sure to turn them. This isn't like
roasting some other dishes, for example, where you put the food in and
leave it unattended until done.
When ALL areas are blackened, put them into a plastic bag (or bowl
covered tightly) to steam for 15 minutes (I've refrigerated them overnight
and they were fine .. the idea is just to cool, steam and loosen the skins,
really). Some suggest a paper bag but the juices leak out and are lost and
messy. I've never had a problem with the plastic melting, though the
peppers are VERY hot.
When they're cool enough to handle, the black skin peels right off
(over a bowl, the juices are worth saving) and you are left with the soft,
slippery, marvelously flavorful roasted pepper. Some say to peel them
under running water but why wash away delicious juices? .. instead just
wait until they're cool enough). Remove inside ribs and seeds and you have
a gourmet miracle on your hands.
If you're still curious about whether or not you've got the right
texture and taste, buy a small can/jar of them (just know that yours will
be better) .. or if you've used canned whole green chiles for Mexican food,
the texture (and technique to do at home) is very similar.