I've got a hybrid setup where I have the Roku wired to a gaming adapter and then wireless to the DIR-655.   Are you using DHCP or static ip addressing?   I set my Roku up with a static IP address and I configured the default gateway as the router.  It you are using DHCP, I would give static IPs a try.   To answer the previous poster, Roku disables the wireless when it senses as wired connection, so it is impossible to use both at the same time.