ok

sudo gainroot
(which is apparently still working, if not.. job done! )
- this one still works

dpkg -l |grep rootsh
(make sure it isn't installed anymore)
- it's still installed

chmod 755 /usr/sbin/gainroot.old
chown root:root /usr/sbin/gainroot.old
mv /usr/sbin/gainroot.old /usr/sbin/gainroot
I run these and the old file is replaced. However, rootsh is still installed and even after a device restart I'm still able to gain root. Also in the package manager, rootsh is still shown as installe.