The Roku works fine when plugged directly to the TV. When auto-detecting the video quality of the screen, it goes to 1080p.Is the Video Processing on teh AVR set to "Processing" or "Through?" If you enable on screen info, does the AVR display what input video resolution/framerate is coming from the Roku? What kind of video output is the Roku set to? Have you tried plugging the Roku directly into the TV.
When the Roku is attached to the receiver, I went to "Option", then "Signal Info", and it lists 1080p for both the HDMI in and HDMI out. When the DirecTV box (the one that work) is selected as the input, it lists 1080i for both the HDMI in and out.
I'm not sure where to find "processing" vs. "through" in the receiver settings. Could you point me in the right direction?