Alex, What about using an IRLINC Transmitter (2411T)? http://www.smarthome.com/irlinc-transmitter-insteon-2411t-insteon-to-ir-converter.html
Have you tried one of those? I don't have the network module for my ISY and I'm thinking for the price, this is a better option. (The Global Cache WF2IR you mentioned is $111.00 at the cheapest place I found online. The IRLINC is $89.99).
Please advise, as I would really like to automate my Roomba!
Thanks,
atomicbear
(If it ain't broke - FIX IT ANYWAYS!)