You should avoid symlinks, it can make nasty bugs to appear... one day. And very hard to debug.

Use mount --bind:

# as root
cp -a /root /home/
echo "" >> /etc/fstab
echo "/home/root /root none defaults,bind 0 0" >> /etc/fstab

# do it now
cd / ; mv /root /root.old; mkdir /root; mount -a

it will be made at every reboots which you should do now if you want to catch errors soon ///

Better to use rsync -a /root /home/ instead of cp -a because cp will not copy hidden files.