Ah, but if one selects Applications in the cloud instance UI, there is a Manage Roles button (for applications other than the default FusionAuth one). In that view, the Add button opens a modal with form fields corresponding to the role attributes described at https://fusionauth.io/docs/v1/tech/core-concepts/roles#role-attributes
I believe I should use the following settings:
SuperRole = on
Default = off
Name = <applicationName>SuperRole
Then I can follow the steps in Dan's list above to assign the role to the user.