I went through the PoststreSQL setup yesterday and I verified my user admin has access to the role dba (see below):
postgres@osboxes:/home/mysuser/projects/gvmd$ psql gvmd
psql (9.6.15)
Type “help” for help.gvmd=# create role dba with superuser noinherit;
ERROR: role “dba” already exists
gvmd=# grant dba to admin;
NOTICE: role “admin” is already a member of role “dba”
GRANT ROLE
gvmd=# create extension “uuid-ossp”;
ERROR: extension “uuid-ossp” already exists
However, in the meantime a colleague of mine noticed I was using a regular user, instead of the Linux superuser.
Now everything works as expected. I can spawn gvmd and create/modify/delete objects like users, tasks, etc.