If you are genuinely logging in as root or su'ing on Ubuntu then your current directory will be changed to root's home directory which is /root.
There are no files in that directory that will show up in a normal ls result. Try using ls -ar to show hidden files/directories also.
This should give you an idea:
You don't need to cd to a directory to ls it.
crypto@ubuserver:~$ sudo su - ## take an interactive root session
root@ubuserver:~# ls ## N.B. dir is now ~ (home) for user root
root@ubuserver:~# pwd ## Where is root's home?
root@ubuserver:~# ls -ar ## no output from the above ls use -a with ls to include hidden
.VirtualBox .profile .debtags .bashrc .bash_history .aptitude .. .
root@ubuserver:~# ls -r /etc ## ls /etc without cd'ing there first without -a
zsh_command_not_found popularity-contest.conf hosts.allow
xml pm hosts
X11 perl hostname
wpa_supplicant passwd- host.conf
wgetrc passwd hdparm.conf
w3m pam.d gshadow-
vim pam.conf gshadow
vbox opt grub.d