Is the goal to enumerate all user roles and groups? There isn't an API to do that in the custom task interface. You would have to write your own metadata queries by using the OMI interface.
You can get a handle to this in a custom task via the SAS.Tasks.Toolkit:
SAS.Tasks.Toolkit.Helpers.SasMetadataProfile.GetActiveProfile().GetSasMetadataConnection()
Cast the result to SAS.IOMI. You will need to add a reference to the SASOMIInterop.dll in the EG application directory.
Chris