Preheat oven to 350°. Heat canola oil in a large skillet over medium heat. Add onion; sauté 2 minutes. Add minced garlic and chopped chipotle chile; cook 2 minutes. Add 1 cup chopped tomato and chopped cilantro stems; cook 2 minutes. Add shredded pot roast and 1 cup sauce from Traditional Beef Pot Roast with Carrots; cover and simmer 5 minutes. Divide beef mixture among tortillas; place, seam side down, in an 11 x 7-inch baking dish coated with cooking spray. Pour 1/2 cup sauce over tortillas; sprinkle with cheddar. Cover; bake at 350° for 30 minutes. Turn broiler to high. Broil, uncovered, 2 minutes. Top with 1/2 cup chopped tomato and cilantro leaves.