If you would like to modify the default s2Member Roles/Capabilities, see: Enhanced Capability Manager.
However (please NOTE): s2Member Support Reps will not offer support for a site that is running modified Roles/Capabilities. If you customize your installation you will be responsible for debugging anything that may not be working as expected. Please see our Support Policy for clarification on this.
If you do modify your Roles/Capabilities, please be sure to install this MU plugin (see below) to prevent s2Member from resetting your customization in the future—should you attempt to update your copy of s2Member or s2Member Pro. This will lock-in your customizations; telling s2Member NOT to reset your Roles/Capabilities during future plugin updates.