Hi, @Peter Koller If the Admin has created the custom role, then with the admin access you should be able to drop. as we have limitation on Postgres 16, please check the below document.
Previously roles with CREATEROLE privileges could change many aspects of any non-superuser role. Such changes, including adding members, now require the role requesting the change to have ADMIN OPTION permission. For example, they can now change the CREATEDB, REPLICATION, and BYPASSRLS properties only if they also have those permissions.
https://www.postgresql.org/docs/16/release-16.html
Regards
Geetha