Hi,
I have uploaded a new object-oriented Arduino interface library for iRobot Roomba and iRobot Create platforms.
Over the years, a number of people have had many problems trying to get Arduino and Roomba to talk to each other. The documentation includes detailed instructions and circuits for overcoming the usual serial comms problems between Arduino and Roomba/Create.
There are example programs, including one that shows how to use my RCKit library, a WiFi shield and the RCTx iPhone app so you can control a Create from your iPhone.
Details and full documentation at Roomba: Roomba library for Arduino