The average gas price in Santa Rosa is down 12-cents in the past week. It’s now at $4.50 per gallon. A month ago, it was $5.44. Santa Rosa is still above the statewide average of $4.37. The average gas price in Santa Rosa is 32-cents cheaper than what it was a year ago at this point. The cheapest gas in Santa Rosa is at the ARCO on Guerneville Road, where a gallon of unleaded is $4.05.