Speaker can turn his camera and microphone on and off, can speak up with a report, download and demonstrate files.
The viewer can chat, listen and view the content of the conference.
There are several ways to select a role for the participants: when you create a scheduled or permanent event in the form of creating an event, choose a role for participants: Speaker or Viewer.
When you invite participants by email from the conference room, select the role: Speaker or Viewer.
Note: the default role is Speaker.
A chort video tutorial:
You can also change the participant's role in the conference room. More information about roles and change roles you can be found in this article.