I roast mine in a lightly oiled enamled cast iron skillet over medium heat. If using a lighter weight pan, you might go a little higher on the heat. I cut them in half, roast skin side down, and then flip once they start to show some color. Repeat on other side. If they get a little burned, don't fret. It's almost like roasting red peppers or poblanos. They're getting blended, and it'll add some smokey flavor to the salsa. They get a little more mushy, but the roasting seems to cook off some of that green acid-ish flavor and make them more sweet.
One Mexican cook also told me that even after the salsa is complete, some cooks will cook they're salsa in a pan for a short time to meld flavors better. Haven't tried this one yet.
Here's a quickie recipe: (From memory, use as a rough guide)
1 lb green tomatillos, halved and roasted (Remove husk and give a quick rinse of course)
5 or so cloves of garlic, roasted in the pan with the tomatillos
a handfull of DeArbols (ymmv go as nuts as you like)
Roast the tomatillos and garlic in an oiled skillet over medium heat until brown/blackened on both sides. Toast chiles over medium lowis heat until they become aromatic. Toss the whole lot in the blender and salt to taste.
This recipe makes a good bit of salsa, so feel free to halve it. If you like more spice, throw in Habs. Get crazy! Throw in cilantro, lime juice, tomato, whatever. But this recipe is a great base to play with.
