Since most if not all distributions /home is owned by root anyway just running the command as posted should not of caused any problems. If you ran the command recursively then yes everything within /home will be owned by root.
I was surprised that Manjaro would let you login as root via the GUI if you select not listed from the log in menu. I have manjaro 19.0.2 running as a VM. Log in as root and change the ownership back for your user's home directory. Permissions should remain the same.