As you may know you can find the Roku IP address by looking at the Roku Settings->PalyerInfo->IP address.
and you may also noticed my earlier post regarding using an Webapp http://www.apps4tv.com/remoku/ to control Roku.
But what if you lost your remote or it is not near to you. I am following this simple trial and error process.
Most of the times my Roku IP address dynamically changing to one of these IP addresses for my eHome wireless G router.
If you are not switching off the Roku device then the IP address wont be changing.