installing tsearch 2 error no user "root"

Hi guys...

very new to postgres.

just downloaded latest stable postgres release.

need to install tsearch2, and i see the tsearch2 is already on the
/contrib folder of postgres.

http://www.sai.msu.su/~megera/postgres/gist/tsearch/V2/docs/tsearch-V2-intro.html

followed the instruction there on how to install tsearch2:

gmake
gmake install
gmake installcheck

but ofcourse, i get an error:

-------------------
[root(at)localhost tsearch2]# gmake installcheck
gmake -C ../../src/test/regress pg_regress
gmake[1]: Entering directory
`/home/hstudy/postgresql-8.1.1/src/test/regress'
gmake[1]: `pg_regress' is up to date.
gmake[1]: Leaving directory `/home/hstudy/postgresql-8.1.1/src/test/regress'
/bin/sh ../../src/test/regress/pg_regress --dbname=contrib_regression
tsearch2
(using postmaster on Unix socket, default port)
============== dropping database "contrib_regression" ==============
dropdb: could not connect to database postgres: FATAL: role "root" does
not exist
============== creating database "contrib_regression" ==============
createdb: could not connect to database postgres: FATAL: role "root"
does not exist
pg_regress: createdb failed
gmake: *** [installcheck] Error 2
-------------------

I started postgres:
---------------------------
[root(at)localhost postgresql-8.1.1]# su - postgres
-bash-2.05b$ /usr/local/pgsql/bin/postmaster -D /usr/local/pgsql/data
LOG: database system was shut down at 2005-12-17 10:34:14 MST
LOG: checkpoint record is at 0/33AD58
LOG: redo record is at 0/33AD58; undo record is at 0/0; shutdown TRUE
LOG: next transaction ID: 571; next OID: 16385
LOG: next MultiXactId: 1; next MultiXactOffset: 0
LOG: database system is ready
LOG: transaction ID wrap limit is 2147484146, limited by database
"postgres"
---------------------------

any idea what i should be reading or doing now?

Thanks very much in advance and Merry Christmas!

-David