Superuser access for Heroku Postgresql?

I'm a long-time Oracle DBA moving over to take on other things, recently
becoming involved
with Heroku Postgres. I've not worked with Postgresql before.

From what I've seen, it does not look like superuser is available. The
"postgres" role is locked
down, and the owner of the database provisioned does not have a number of
privileges,
including superuser. My understanding is that by default, you need to
use O/S authentication
to access the postgres role; and with Heroku you do not have that.

What is the situation here? It looks as though why I can do things such
as add extensions,
add schemas, and so on; but I cannot add roles. It seems as though you
get that one database
with it's owner, and that is it. And everyone who needs to work with
this database uses that
same owner/password.

Heroku documentation is not forthcoming on how their add-on flavor of
Postgresql differs from a
functional POV from a full-blown local setup.

Thanks,
JDT