Cut the stems off of each jalapeño, then slice each pepper in half lengthwise. Carefully remove the membranes and seeds from the inside of each pepper.
Lay the jalapeños, cut side down, onto a baking sheet. Broil for 4-5 minutes until charred.
Immediately transfer the roasted jalapeños to a paper bag, and seal shut. Allow the jalapeños to steam in the bag for 15 minutes.
Remove the jalapeños from the bag, and peel the skins off of each one.
Refrigerate roasted jalapeños in an airtight container for up to 5 days, or freeze for up to a month.