The calculated distance (air line) between Frankfurt am Main and Rosbach vor der Höhe is approximately 13 miles respectively 21 kilometers.
By car or train, the actual journey to Rosbach vor der Höhe is certainly longer, as only the direct route (as the crow flies) between Frankfurt am Main and Rosbach vor der Höhe has been calculated here.
Air line (approximately)
21 kilometers
11 nautical miles