Click on REPORTS (in the menu on the left), you can select USAGE REPORTS, and then click on USAGE.

There, you will be prompted for a date range (can only be one month/30 days). Once you run the search you will get a list of all of your meetings and it will show the number of attendees in the PARTICIPANTS column:

Click on that PARTICPANTS number and a pop-up will list everyone, giving you an option to export to Excel:

It will show you the time when someone joined, when they left, and how long they were on the call for, along with other metrics.

But the best part? No more having to take roll call or have a teammate do that while you are running the meeting. Review that information after the fact.