Preheat oven to broil and place rack within the top-third of the oven.
Brush a large sheet pan with a thin layer of oil then lay the red bell peppers on their side on the pan. Broil for 5-7 minutes per side, or until nicely blackened all around. Remove from oven and place in a large bowl and cover tightly with plastic wrap. Allow to cool completely, around 1 hour.
Peel the skin and remove the seeds from each pepper, keeping them inside the bowl they cooled in. Place peeled flesh in a second, large bowl until all peppers have been peeled. Place a sieve or chinois over the second bowl and slowly add the peeled skins, seeds, and any water from the bottom of the first bowl and strain the liquids into the bowl with the flesh until none remains. Discard remaining solids from the sieve.
Place bell pepper flesh and liquids into a high-powered blender and puree until smooth, then add to a large, dry pot and cook over low heat, stirring every 20-30 minutes, until reduced by half, about 2 hours.
Add roasted red bell pepper paste to jars and top with ¼-inch of olive oil for preserving and canning. Store sterile-sealed jars in the pantry for up to 1 year, and opened jars in the fridge for up to 10-14 days.