Pour juices from beef roast into large saucepan or saucepan; set meat aside. Add carrots and 1 cup water to saucepan; bring to boiling. Reduce heat and simmer, covered, 3 minutes. Add remaining water, potatoes, tomatoes ,and 1 tablespoon oregano. Return to boiling; cover. Simmer 3 minutes or until vegetables are tender. Break beef into bite-size pieces and add to stew; heat through. Season with salt.