Preheat oven to 450 degrees. Cut each pepper in half, remove seeds and flatten with the palm of your hand. Place peppers, skin side up on a baking sheet, brush with olive oil. Roast peppers until the skin blisters and chars. This will take between 15 - 25 minutes, watch closely. Remove peppers from the oven and place in a plastic bag to steam for 10 minutes. Remove from the bag, the skins will remove easily, slice peppers into strips. In a large bowl combine the shrimp, peppers, red onion, and capers. Mix all of the marinade ingredients together. Pour over shrimp mixture. Stir to coat. Refrigerate at least 8 hours and up to 48 hours. Stir often while in the refrigerator. When ready to serve, drain the shrimp mixture and serve.