Check out the Santa Rosa Visitor's Center website. There is so much to do in Santa Rosa, and this website lists it!
http://www.visitsantarosa.com
Looking for Wine Tasting? Santa Rosa is centered in Sonoma County, famous for its vintages.
Into Cycling? Santa Rosa is the host to a number of exciting Cycling events.
Looking for Art and Culture? Santa Rosa has a number of museums and music venues.