Rosny was named for a family name of W.A. Bethune, the holder of the original grant on the point, and he named it after his ancestor, the Duc de Maximilien de Bethune Sully, of Rosny-sur-Seine near Mantes in France.
Rosny is a pretty, quiet, residential area, with sweeping views of the Derwent River and its estuary, the Tasman Bridge and Mount Wellington, and looks directly across the river to the CBD of Hobart. It features no commercial facilities except for a local store, and is located on a narrow peninsula which juts out from the eastern short to culminate at Rosny Point. From the shore it climbs the rising slopes of Rosny Hill.
Much of Rosny is given over to thick groves of local she-oaks, which line the foreshore, interspersed with radiating residential streets. A twisting and undulating bike path also follows the shoreline all the way from neighbouring Montagu Bay into neighbouring Rosny Park before heading in the direction of Bellerive.