Heat the oil in a large pot or Dutch oven over medium heat. Add the onion, salt, and black pepper; cook, stirring occasionally, for 7 minutes. Add the carrot and potato; stir and cook for 2 more minutes. Add the tomatoes, garlic, oregano, thyme, rosemary, and red pepper flakes. Stir in the broth and bay leaf. Bring to a boil, then reduce the heat to a simmer and cook, covered, for 20 minutes.