Root's .bashrc not executing on sudo -i

You should look at the presence and content of the file /root/.profile.

The init file ~/.bashrc is not sourced in login shells: on Ubuntu it is sourced from ~/.profile

Furthermore, the file /root/.profile is not copied from /etc/skel/ as for other users, it is instead copied from /usr/share/base-files/dot.profile during installation of package base-files.

There is one additional situation which you should keep in mind, which happened in my case.

If you would create .bash_profile file then this file is taking over the responsibility to load / execute .bashrc or .profile .

When you open your terminal and use "sudo -i" and you are suddenly missing some command aliases, file list coloring etc., then double check if this file is present in your home directory, then rename it and reopen your console again. This should fix it.