You have to pass those environment variables to Firefox through sudo.
sudo has a --preserve-env=list option but you must know the value for DBUS_SESSION_BUS_ADDRESS. That's usually
unix:path=/run/user/1000/bus
where 1000 is the id of the user Firefox is running for. Your root console could have no DBUS_SESSION_BUS_ADDRESS or have a different value for it.To be 100% sure of the value, as you are root you could look into the environment of one of the running Firefox processes. Or wrap Firefox in a script that echoes that variable to a file before starting the browser.