Since the latest udev update (udev-210.1453291613.c8d5bdf-25.30.1.x86_64,
installed on 2016-01-29) that unit does not start anymore.

All I can see is the following error in my system journal:

Jan 31 12:45:55 cloud systemd[1]: Cannot add dependency job for unit
systemd-udev-root-symlink.service, ignoring: Unit
systemd-udev-root-symlink.service failed to load: Invalid argument. See system
logs and 'systemctl status systemd-udev-root-symlink.service' for details.

but then, with journalctl or systemctl I don't see anything else besides that
message.

On closer inspection I'm guessing that there is a syntax error in the unit
file:

ExecStart=@udevlibexec@/rootsymlink-generator