You roast sweet peppers in the oven by tossing sliced pepper strips in olive oil, salt, and black pepper before spreading them evenly on a baking sheet. Roast them at four hundred degrees Fahrenheit for about twenty to twenty five minutes until the edges become tender and lightly charred. Alternatively, you can roast whole peppers directly over an open flame or broiler until the skin blisters completely. Place the charred peppers in a covered bowl for ten minutes to easily peel away the outer skin.