Roasting a pepper held with tongs over an open flame simply chars the outside of the pepper. This is fine if you like eating semi-raw peppers that are singed in spots, but it's not fine if your goal is to get a silky-soft pepper that slumps on a plate, sweet and aromatic. To achieve that, follow these directions:
Preheat your oven to 375 degrees Fahrenheit. While the oven is preheating, line a half-sheet pan with aluminum foil. Wash 4 bell peppers. (I use exclusively red and yellow peppers). Leave their stems on, you'll use them as little handles later in the roasting process. Place the four peppers on the sheet, leaving a bit of space between them. Place the sheet in the oven.
Every 20 minutes, open the oven and, working quickly, turn the peppers using their stems, so that they aren't lying on the same side throughout the entire roasting period. You'll notice each time you move the peppers that their skin has started to wrinkle and blister, even turning brown and puffing up in spots. Try to make sure that the peppers rotate evenly throughout the process.
Open the oven and check the peppers. They should be evenly browned and blistered, collapsing in on themselves a bit. Place the sheet on a cooling rack and let the peppers cool. Don't try to fiddle with them just yet - the liquid inside the peppers is amazingly hot. Be patient.
When the peppers have cooled for about 20 to 30 minute, start to peel them. The peel should generally slip right off, but the peppers themselves will be quite slippery, so you'll need to do this with some care. I like to gently split the peppers and work with large sections at a time, simultaneously dumping out any of the interior liquid and, of course, ridding the peppers of all their seeds. This can get messy - I suggest working over a lipped cutting board and having a clean plate ready for the cleaned, peeled pepper segments.