So you mean without entering the "superuser" boot option? The /root/.profile file controls this feature. It will autologin as root if the /etc/sysconfig/superuser file is present, so there are multiple ways to achieve this:
1) If you don't already have a backup file, then execute the following
touch /etc/sysconfig/superuser
tar czf mydata.tgz /etc/sysconfig/superuser
Place the mydata.tgz in the appropriate location so it will be loaded automatically.
2) If you already have a backup file, then boot with the superuser boot option, add the following line to your /opt/.filetool.lst, and create a backup:
etc/sysconfig/superuser
3) Create a pseudo-extension (requires squashfs-tools extension to be loaded):
cd /tmp
mkdir -p superuser/etc/sysconfig/
touch superuser/etc/sysconfig/superuser
mksquashfs superuser superuser.tcz
Place superuser.tcz in the appropriate location so it will be loaded automatically.
4) Add this line to the top of /opt/bootlocal.sh (may not work due to timing)
touch /etc/config/superuser
If you need help understanding the backup file mydata.tgz or help creating extensions, the wiki can explain or you can ask here.