Rosasco is a comune, or municipality, located in the Province of Pavia within the Lombardy region of northern Italy. It is situated approximately 50 km (31 mi) southwest of Milan and about 45 km (28 mi) west of Pavia.
As of December 31, 2004, the municipality covered an area of 19.8 km² (7.6 sq mi) and had a recorded population of 691 residents.