The calculated distance (air line) between Konstantinovsk and Rostov-on-Don is approximately 69 miles respectively 112 kilometers.
By car or train, the actual journey to Rostov-on-Don is certainly longer, as only the direct route (as the crow flies) between Konstantinovsk and Rostov-on-Don has been calculated here.
Air line (approximately)
112 kilometers
60 nautical miles