While there are HDCP "strippers" the cost is that of another 24 inch TV (they seem to sell for 99 bucks here.)
Another exit is the older Roku with the composite cable. Rare and hard to find now.
You left out both the model numbers of the TV and Roku.
I bought a ROKU to hook up to my 8 year old 24 inch Polaroid HD TV and it will not let me stream Netflix without an "Unauthorized" covering the screen. I get sound and the picture around the big sign and can even see the whole picture if I rewind. ROKU says my TV cannot use the newer standard HDMI cable . Is there any fix for this without reconnecting to Comcast cable? The TV works fine with cable and has a tuner in it. Any sugestions appreciated.