The .xinitrc displayed in the screenshot is not completely correct. This is better:

#!/bin/sh

SHELL=rc /usr/local/plan9/bin/9 rio &
/usr/bin/roxterm &
exec /usr/bin/gkrellm -g +0-0

By the way, you don't need roxterm to run plan9port. Any terminal emulator will do for keeping your regular *nix environment around.

A little warning: you can open something similar to a terminal emulator within acme using the internal command "win". It's very useful, but don't try to compile latex documents from that commandline. Latex will get stuck in an infinite loop. It's wiser to use your regular *nix terminal for running programs that aren't part of plan9port.
edit: use "win bash" and latex will work fine
edit 2: or not. What's going on here?

Also, note that in my configuration the "shell" started both by rio (the window manager) and acme's win is "rc", not your regular "bash", and a different path than you would expect is used too:

% which ls
/usr/local/plan9/bin/ls

That means the commandline will behave very different from what you expect!