I used to do that. Now I create SFDC campaigns and add registrants to a campaign for each event.
The other thing I previously did was create a timestamp for each registration, make it active in RCA, and create a report of anyone with a value for that timestamp. You can the schedule that report to automatically email on a schedule of your choosing in the analytics section.
Thanks @Chris - they do sync to Salesforce as registered members of the campaign, it's just I have external stakeholders who don't have SFDC access. The shared Google Sheet works great, I just want it to pull in the registered leads for each campaign instead of me having to manually export/download/upload each time to refresh the registrants list.