You can contact the Clackamas County Tax assessor in Oregon City. The county doesn't include bedrooms if they don't have a closet and a window large enough for ingress and egress. Be careful though because if the tax assessor increases the number of bedrooms, your property taxes "may" go up.... more
If you can prove the information is incorrect, then you should be able to get the public record changed. You will have to contact the agency that holds and reports the information you want changed. In Clackamas County, that could involve contacting multiple agencies, such as the County Assessor and the Department of Transportation and Development.
Sometimes, attempting to change the record can cause more trouble than it's worth. As Ms. Levinson indicated below, incorrect information in public records sometimes results from a prior occupant making changes to a dwelling without obtaining the required permits.
If you were to provide more information. It would be useful in answering your question.