Most listings are in the $10's per square foot per year. The Rohnert Park region is going through a decline in rates. In the last 3 months, the median rate decreased $6 per sqft per year. That's a 23% decrease in rent.
Compared to the rest of the Bay Area market, the Rohnert Park region has smaller rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 43 listings have come on the market, so you'll want to check back regularly for new listings. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,620 sqft. Most properties in this market are approximately 1 floors. Most buildings in this area were built in 1987 and are Class B.