Most listings are in the $10's per square foot per year. The Rohnert Park submarket is experiencing a a boost in rates. In the last 3 months, the median rate went up $17 per sqft per year.
Compared to the rest of the Bay Area market, the Rohnert Park submarket has lower rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 10 listings have been listed, which means office spaces are probably leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 300% of the listings in the Rohnert Park are subleases, so you might be able to find a shorter term or below market rent. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,500 sqft. Most buildings in this area are close to 2 stories. Most buildings in this region were built in 1985 and are Class B.