Data driven subscription permission issue

Hi,

There's a requirement for users who are not report server administrators to be able to create data-driven subscirptions.  When they attempt to create this subscription, they get a permission insufficient error.  I've read in MS docs that Data-driven subscriptions are typically created and maintained by report server administrators.  As the report server administrator, I can create the subscription with no problem.  However, I do not want to give users admin access.  In this article: https://docs.microsoft.com/en-us/sql/reporting-services/subscriptions/create-modify-and-delete-data-driven-subscriptions?view=sql-server-2017, it mentions that the author of the subscription must have permission to "Manage reports" and "Manage all subscriptions. I think this can be accomplished by creating a custom role. 

I've tried following this article: https://docs.microsoft.com/en-us/sql/reporting-services/security/role-definitions-create-delete-or-modify?view=sql-server-ver15. To create a role definition in SSMS, I go to the reportserver database>expand the Roles folder. I only see a Database Roles folder and an Application Roles folder.  How do I assign the "Manage reports" and "Manage all subscriptions permissions to a role? Also, I do not see the predined roles in the Database Roles folder or the Application Roles folder.  Is this the right location?