Speaker roles can designate the speakers in a session - making it clear to attendees who are moderators, speakers, etc.
After you have uploaded the speaker role(s) with their associated individuals you can change the labels of your roles via the event admin site.
Navigate to your event admin site: https://admin.core-apps.com/SHOWCODE
Click into the Speakers module from the top toolbar
Select Edit Roles from the lefthand menu
Here you can edit the speaker role labels in which you have already uploaded, which will update that label for all records tied to that role.