How to restore roles without changing postgres password

Hi!

How to create backup script which restores all roles and role memberships 
from other server without changing postgres user password.

I tried shell script

PGHOST=example.com
PGUSER=postgres
PGPASSWORD=mypass
export PGHOST  PGPASSWORD  PGUSER
pg_dumpall --roles-only --file=globals.sql
psql -f globals.sql postgres

but this changes user postgres  password also.
How to restore roles so that postgres user password is not changed on 
restore.

Script runs on Debian 10 with Postgres 12
Server from where it reads users runs on Debian Squeeze with Postgres 9.1

Andrus