Most listings are in the $10's per square foot per year. The Rohnert Park region is experiencing a decrease in rates. In the last 3 months, the median rate fell $2 per sqft per year. That's a 13% decline 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 undervalued submarket.
In the last 90 days, 16 listings have been listed, which means new availabilities most likley are going fast. You'll want to be prepared to make an offer immediately. 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 1,100 sqft. Most properties in this market are approximately 2 stories. Most buildings in this market were built in 1986 and are Class B.