Heat a large saucepan over medium heat and add the oil, diced onion and garlic and saute until the onions are golden, about 5 minutes. Add the tomatoes, pot roast, black beans, chili powder, and 2 cups water. Lower the heat and simmer for 30 minutes. Season with salt and pepper, to taste. Ladle the chili into serving bowls and sprinkle each bowl with 1 tablespoon of cheese. Serve hot.
For Pot Roast:
Season the beef with salt and pepper and lightly coat with flour. Heat the canola oil in a large skillet on medium-high heat and brown the meat on all sides. Remove to a platter and set aside. Arrange the carrots, celery and onion in bottom of slow cooker and top with the seared beef. Add the broth, water, garlic, Worcestershire sauce, and thyme, and set the cooker on low for 8 hours. When finished, remove the meat to a serving platter. Let the vegetables and broth cool for about 5 minutes, then add to a blender. Slowly blend until smooth and transfer to a serving bowl. Serve the gravy with the pot roast and roasted root vegetables.
For Roasted Root Vegetables:
One hour before the pot roast is done cooking, preheat the oven to 400 degrees F. Add all the vegetables to a large bowl and add the canola oil, rosemary, thyme, and onion. Season with salt and pepper, to taste, and arrange on a sheet tray. Roast for 30 minutes, then toss and roast another 30 minutes. Arrange on a serving platter and serve.