Preheat oven to 500 degrees. Line a baking sheet with aluminum foil. Hold 4 raw tomatillos back, but place the rest of the halved tomatillos and the roma tomato skin-side down on the baking sheet. Bake until they begin to toast, about 20 minutes.
In a food processor, combine the roasted tomatillos and tomatoes, the raw tomatillos, jalapeños (start with a half jalapeño if you're not sure, see note 1), red onion, garlic, cilantro, cumin and oregano. Pulse until the mixture is mostly smooth with some texture (see note 2).
Taste and add more chiles and/or seeds depending on your preference for spiciness. Remember, the salsa tastes spicier when warm and when tasted without food. It will be milder after chilling and when eaten with food.
Add lemon and lime juices, and season to taste with salt and pepper (I like 1 teaspoon salt and 1/2 teaspoon pepper). Yield: About 2 cups.
Chili heat: This salsa gets its spiciness from jalapeño peppers. If you're a little shy about spice, add a little bit at a time and taste as you go along. Remember: Salsa tastes spicier when you eat it plain AND when it's warm. So, once this salsa is cold and you're eating it with other food, it will be less spicy.
Pulse for chunky salsa. If you're using a high-speed blender, don't over blend your tomatillos! Keep a little texture in there, so you can see all the lovely colors and charred bits. Your chips will thank you.
Grill: You could also roast the tomatillos and tomatoes on grill. Keep them whole when using coals.
Make ahead: Tomatillo salsa can be made several days in advance and stored in the fridge. Or, freeze for up to 3 months and thaw overnight in the refrigerator (some separation may occur; just shake to recombine).