Preheat oven to 325 degrees F. Heat the oil in a large Dutch oven or deep-sided roasting pan over medium-high heat. Season the roast with salt and pepper, brown on all sides, and then transfer to a plate. Add the onion, bell pepper, carrot and celery to the pan and cook 3 to 4 minutes. Mix in the flour, garlic and tomato paste and cook 2 to 3 minutes more. While stirring, slowly mix in the wine. Add the diced tomatoes, oregano, olives and sugar and bring to a simmer. Place the beef in the sauce. Cover and cook 2 hours in the oven, or until the beef is very tender. Remove the beef from the sauce. Slice and arrange on plates. Spoon the sauce over top the beef and serve.