Hello Martin,
What error are you seeing when you try to delete the repo role in question? Are you seeing a privileges issue here also? If so you can do the following:
Its always helpful to run a trace to see what exact privilege you are missing:
1) Please run the following statement in the HANA database to set the DB trace: alter system alter configuration ('indexserver.ini','SYSTEM') SET ('trace','authorization')='info' with reconfigure;
2) Reproduce the issue/execute the command again
3) When the execution finishes please turn off the trace as follows in the Hana studio: alter system alter configuration ('indexserver.ini','SYSTEM') unset ('trace','authorization') with reconfigure;
If you look into the trace file that is generated after you turn off the trace you can see what privilege you are missing to delete the repo role in question.
For further information please see:
http://scn.sap.com/docs/DOC-68108
Regards,
Michael