So sorry for the late response here, I just saw your replies. Since your User Role field is a list, you won’t be able to manually edit that field through the App Data view in the editor. Any “List of Things” field can only be changed using workflows. For example, the action for changing a User’s List of User Roles could be:
Data --> Make Changes to a Thing --> Thing to Change: Current User --> Field to Change: User Roles add Dropdown of User Roles’s value
As Gaby said, building an admin page would be a great way to edit that field, and create accounts for other Users. You can manually create the User Roles entries in app data and then assign them to the User on the admin page when the account is created for someone else, or later on through different workflows. Additionally, you can set up privacy roles which ensure that only Users who are Admins can view, find in searches, or modify specific data types and fields in your app.