Round Rock is on a roll. On the heels of being named one of the country’s fastest growing cities, the booming Austin suburb has been deemed one of the 10 most livable mid-sized cities in America. This award comes from financial website SmartAsset, which compared 227 U.S. cities based on eight metrics, ranging from median household income to unemployment rate to home value change. (The cities included have at least 100,000 residents; the 100 most populous U.S. cities were removed.) “For Americans seeking a more affordable and less crowded alternative to the bustle of a big city but not interested in very small towns, a mid-sized city might be the best place to…