You may roast peppers in any way you feel that you will have the most success with. It won’t affect the process or safety for canning, dehydrating or freezing.
We find that we prefer a more recent technique that has emerged over more traditionally recommended methods. The more recent approach, for us, seems less time consuming and fiddly, and causes less wastage. But if you have mastered the older methods and they work for you just fine, stick with them!
Our preferred method for roasting peppers
We now use the following method for roasting peppers; it draws on a new technique that Ball has introduced as of its All New Book (2016) for roasting veg:
- Line rimmed baking sheets (balance as many as you think you will need with as many as you can fit in oven at one time) with tin foil (optional but makes cleanup far easier.) No need to spray or oil trays or foil. Set aside.
- Wash, stem, seed the peppers (for hot peppers, you may wish to leave some seeds in.)
- Put on ungreased baking sheet surface cut side down.
- Roast at 190 C (375 F) for about 25 to 30 minutes, until the skin on some of them begins to char. (How long exactly will depend on how hot your oven runs.)
- Remove from oven, leave on tray undisturbed, let cool for about 10 to 15 minutes or until cool enough to handle safely.
- The skin will be wrinkled. Pinch it at one end, and most of the time you will be able to pull it away entirely from the pepper in one go.
- If the skin isn’t that wrinkled, then you need to roast longer. If the skin sticks a lot, then you need to let it cool a bit more.
Using the above method, budget in your mind about 2 hours prep work per half US bushel (5 kg / 11 lbs) of peppers.
More traditional recommendations
These methods have traditionally been recommended by the USDA, as well as many other cooking instructors and cookbooks in the past.
Cut two or four slits in each pepper, and blister using one of the following methods:
- Oven or broiler method: Place chile peppers in a 200 C (400°F) oven or broiler for 6 to 8 minutes until skins blister; OR
- Range-top method: Cover hot burner, either gas or electric with heavy wire mesh. Place chilies on burner for several minutes until skins blister.
Whichever method you used, you then “allow peppers to cool. Place in a pan and cover with a damp cloth. This will make peeling the peppers easier. After several minutes, peel each pepper.”  United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Peppers.
We have always found that either of the suggested above methods leaves us pick-picking little bits of skin off for hours, and wasting a lot of the flesh, though you may have better luck.
How can I preserve these
You may pressure can roasted peppers;
You may dehydrate roasted peppers;
You may use them in other home-canned products calling for roasted pepper.