The calculated distance (air line) between Ryazanskaya and Rostov-na-Donu is approximately 157 miles respectively 253 kilometers.
By car or train, the actual journey to Rostov-na-Donu is certainly longer, as only the direct route (as the crow flies) between Ryazanskaya and Rostov-na-Donu has been calculated here.
Air line (approximately)
253 kilometers
137 nautical miles