There are many good housing options in Santa Rosa and in Rincon Valley, such as apartments or single family homes etc. Summer is the best time to find a rental as this is the time everyone wants to move with sunshine. I suggest looking in the yellow pages for a rental company, the local newspaper "The Press Democrat" is online and the best option is Craigslist under Bay Area in Northbay section. I grew up in Rincon Valley and it is a great place to live. If you have children, the schools are wonderful and they will enjoy their education there.
I have had several out of town clients ask about rentals lately and honestly the best place to look is on Craigslist. We have several rental companies here locally, and almost all listings are on Craigslist. I hope that helps and best of luck with your search! You will love living in our beautiful area. :)