Of course it is possible to add additional roles. There're preset roles created for speakers and moderators. You can create new roles by going to Roles & Access control. You can create roles for general contacts and provide access to content accordingly. You can also create roles for admin users and provide each role with different level of access control in the backend.

Please note that Roles and Access Control option is only available with the super user i.e. the one signed up for the account on Dryfta platform.