The calculated distance (air line) between Fond du Sac and Roches Noire is approximately 9 miles respectively 15 kilometers.
By car or train, the actual journey to Roches Noire is certainly longer, as only the direct route (as the crow flies) between Fond du Sac and Roches Noire has been calculated here.
Air line (approximately)
15 kilometers
8 nautical miles