The calculated distance (air line) between Rouen and Boulogne-Billancourt is approximately 67 miles respectively 107 kilometers.
By car or train, the actual journey to Boulogne-Billancourt is certainly longer, as only the direct route (as the crow flies) between Rouen and Boulogne-Billancourt has been calculated here.
Air line (approximately)
107 kilometers
58 nautical miles