server administration problem: Database startup and permissions

Hi,

I created a database cluster using the following commands as per what is
given in the postgres server administration manual

root# mkdir /usr/local/pgsql/jas
root# chown jsbali /usr/local/pgsql/jas
root# su jsbali
jsbali# initdb -D /usr/local/pgsql/jas

After that i tried to start up the postmaster process using the follwing
command

jsbali# pg_ctl start -D /usr/local/pgsql/jas

It does start the postmaster process.

Then i create a new database here using the following command

jsbali# createdb DBxyz

here in the same user account i try to open pgadmin3 and it doens't

I open pgadmin3 from the root account and try to connect to my local host
and it says

An error has occured:
Error connecting to the server: FATAL: role "postgres" does not exist

Don't know whats going on wrong.
I'm totally confused.

~Jas