As you saw in the previous recipe, SSRS comes with an array of predefined roles that should meet the needs of most of your users. You may, however, find situations in which the predefined roles are not quite right for your needs. SSRS allows you to create new roles, in which you may tune the permissions to suit your needs.
Adding new roles is not done through the Report Portal, as you might expect. Instead, it is handled within SQL Server Management Studio. You must have administrative rights to the reporting server to create new roles.