Place julienne peppers, onion and minced garlic in a bowl and toss with about 1/2 teaspoon of olive oil and a pinch of salt and pepper. Spread out on a sheet pan in a single layer and roast in a 425 degree oven 8-10 minutes and then let cool. meanwhile place thawed corn, black beans, tomatoes and cilantro in a bowl. in another bowl whisk together oil, lime juice vinegar, cumin, salt and pepper. Add cooled peppers and onions to corn mixture. Pour dressing over all and toss to coat. adjust salt and pepper to desired taste.