The User Roles are a feature that Admins of the system can use to give permissions/restrictions to various parts of the CQ to their employees.
Take a look at the definitions for each role before creating another: Definition of each User Role
To add a new custom role or give a user a different role, go to the "Admin Settings" section at the bottom of the screen and click on "Roles" at the top.
You will see the Admin and User default roles already set in there, click on "Add New Role" to create your own.
Give it a name and select the permissions boxes that will apply to this custom role. Click on the tick to create the role.
Next, you will need to select the person who you wish to give this role to and in the "Role" column, use the dropdown box to select your custom made role. Make sure you save the changes you have made by clicking "Save Changes" at the top left of the screen.
To delete a custom role, simply go back in to where you added it, click on the pencil icon to the right of it's name and select "Delete Role".