Roger Stringer, a Twilio expert, has created a roll call feature that allows moderators to take a headcount of participants during a conference call programmatically. This feature can be useful for scheduled conferences where it's essential to ensure everyone has joined before starting. To set up this feature, developers need to create two TwiML files: one for non-moderated callers and another for moderators. The moderator file includes an action that triggers a roll call when pressed, which then presents the list of participants on the screen. This feature is built using Twilio's conference calling functionality and can be customized to fit specific use cases.