Add jalapeños and roast for 30-35 minutes or until peppers are evenly charred. Remove from oven and immediately transfer to a sealable glass container or plastic bag and let sit for at least 15 minutes, or until peppers are cooked through.
Remove stems and skin/peel. You can also remove the seeds if you don't want it as spicy, but I prefer to leave them.
Place jalapeños and remaining ingredients into a blender process until smooth.