The calculated distance (air line) between Rostov-na-Donu and Kropotkin is approximately 130 miles respectively 210 kilometers.
By car or train, the actual journey to Kropotkin is certainly longer, as only the direct route (as the crow flies) between Rostov-na-Donu and Kropotkin has been calculated here.
Air line (approximately)
210 kilometers
113 nautical miles