The calculated distance (air line) between Rostov-na-Donu and Krasnodar is approximately 155 miles respectively 250 kilometers.
By car or train, the actual journey to Krasnodar is certainly longer, as only the direct route (as the crow flies) between Rostov-na-Donu and Krasnodar has been calculated here.
Air line (approximately)
250 kilometers
135 nautical miles