Follow the below given steps to recover the opensuse root password

1. boot the system with any livecd
2. suppose you have the following partition structure
sda1 /boot
sda2 /
sda3 swap
sda4 extended
sda5 systemvg ( volume group containing physical volume --- LVM)
usrlv /usr
optlv /opt
varlv /var
tmplv /tmp


3. mount the partions as given below

mount /dev/sda2 /mnt
mount /dev/sda1 /mnt/boot
swapon /dev/sda3
vgchange -ay
mount /dev/systemvg/usrlv /mnt/usr
mount /dev/systemvg/optlv /mnt/opt
mount /dev/systemvg/varlv /mnt/var
mount /dev/systemvg/tmplv /mnt/tmp

mount -o bind /dev /mnt/dev
mount -t proc none /mnt/proc

chroot /mnt /bin/bash


4. now change the root password as mentioned below

passwd root

If there is some problem while doing the chroot then do the following

Umount /mnt/dev
umount /mnt/proc

And run the following command
mount -o bind /proc /mnt/proc
mount -o bind /sys /mnt/sys
mount -o bind /dev /mnt/dev