Roasio is a comune (municipality) in the Province of Vercelli in the Italian region Piedmont, located about 80 km northeast of Turin and about 35 km northwest of Vercelli. As of 31 December 2004, it had a population of 2,517 and an area of 28.1 km2. The municipality of Roasio contains the frazioni (subdivisions, mainly villages and hamlets) San Maurizio, Castelletto Villa, San Giorgio, Sant' Eusebio, Corticella, Curavecchia, and Prucengo. Roasio borders the following municipalities: Brusnengo, Curino, Gattinara, Lozzolo, Rovasenda, Sostegno, and Villa del Bosco.

Demographic evolution