Preheat the oven to 450 degrees. Cut the peppers in half and remove the stems and seeds.
Place the peppers cut side down on a parchment lined baking sheet. Lightly coat with oil, if using. Roast for 20 minutes, or until the skins blister and peppers have collapsed.
Immediate place the peppers into a ziploc bag and seal the bag shut tight. Allow to steam for 30 minutes.
Remove the peppers from the bag and peel the skin from the peppers. Discard the skin and store the peppers as desired.