Melt the butter in a large pot over medium heat, and mix in the olive oil. Saute the onion, carrot, and celery for about 5 minutes, until onion is lightly browned. Stir in the garlic, and continue to cook 1 minute. Mix in the flour. Whisk in the chicken broth, and bring to a boil. Place the potatoes in the pot, reduce heat to low, and cook 15 minutes, until potatoes are tender.
Mix the half-and-half into the pot. Stir in the roasted red peppers. Season with thyme, salt, and pepper. Continue cooking until heated through.