The name derives from the Latin name "Rosius. A town located at 870 meters of altitude, not far from Aosta, at the mouth of Valpelline in the Valley of the Great St. Bernard, Roisan-Saint-Oyen is composed of several villages set on terraces. The town stretches from the valley basin, where the stream Buthier flows until it reaches Becca di Viou, surrounded by orchards and vineyards and in a privileged location similar to other realities such Aosta itself and the areas of Monte Emilius and the Grand Combin.
The first settlements are probably related to the old path, along the left side of Buthier, which joined Aosta to Colle del Gran San Bernardo. The trail was originally controlled by the Salassi, the first inhabitants who populated the region in pre-Roman times. This population was formed by the union of the tribes of the Celts, that arrived in the area from central Europe, between the VIII and V centuries B.C., with the local people: The Salassi were defeated by the Romans, that arrived in the area in the I century. Of the Roman presence remain the funerary inscriptions, inserted, in the XVII century into the base of the altar of the church of San Vittore, which at present is the seat of the Regional Archaeological Museum. From the XII century, the jurisdiction over the area of Roisan was divided between the Lords of Rhins linked to the Bishop of Aosta, and the Lords of Quart, which ruled over a larger portion of the town. According to a popular tradition in 1536, the famous Italian writer Calvino sheltered here during his escape towards the Valais.

Not to miss:

The Parish Church of San Vittore, dating from the XV century, dominates the town. On the façade a fresco depicting St. Victor, a Roman soldier martyr. The Romanesque bell tower with two floors of mullioned windows was probably built on an existing tower. Inside the parish preserves some wooden statues of great value representing San Vittore and 2 groups of the Madonna and Child and a series of paintings dating from the XIII and XIV centuries.
The fortress house of the Rhins, which dates back to 1100 and belonged to this Family that ruled the fief for the Bishop of Aosta. Although currently it is used as a farmhouse, there are still visible traces of the characteristics of a stronghold.
The Chapel of Martinet.
The Chapel of St. Philip Blacks.
The Chapel of San Michele.
The Church of St. Bernard and Our Lady of Good Help in Blavy.
The Chapel of St. Thomas in Cantebury.