I am not able to get screen mirroring (aka AllShare cast in past) working with my Samsung S3 and Roku HDMI stick attached to my TV. Everything works fine but I just get a black screen on TV. I can hear the sounds of taps and it seems the devices are properly connected but it would just refuse to display any picture on TV.
I have got my phone rooted and added wlan.wfd.hdcp=disable in build.prop file. Earlier I was getting HDCP not supported error but I fixed it by adding this line.
I cannot make head and tail of this problem and banging my head against wall for two days. There is no error displayed anywhere which makes it harder to troubleshoot. I can screen mirror correctly with my Samsung Tablet so there is no problem with Roku at other end.