If you still have the root password it won’t be that difficult to perform a PASSWD command, otherwise you may try and access the disk from external source and then hope that JohnTheRipper or similar tools can find the password.
Boot the system from the SUSE media in rescue mode. You could also use Knoppix or a Centos LiveCD. Mount your root partition on /mnt. Edit /mnt/etc/shadow and remove the root password (the long string of random-looking characters between the frist colon and the second colon). Remove the rescue media and reboot. Log in as root. The root user now has no password – just hit <ENTER> when prompted when you login. Use the “passwd” command to set the root password and to set any other passwords you like.