Import CSV list of servers into RDM

Hello!
Traditionally I've maintained RDM as well as a separate list of servers via a CSV file. I'd like to move away from the CSV file and import any servers on the CSV but not in RDM already. Does anyone have and ideas on how to best loop through both RDM and the CSV and create RDM entries for those that don't have on already? The CSV also has some other info such as Department and Use that I'd like to import as custom fields, so if those can be imported as well, that would be a bonus!
Thanks,