Since I was able to cast from my Windows 10 PC to my Samsung TV, but not the Roku I figured the problem was with the Roku. When I try casting sometimes the TV pops up asking to allow which i do. It appears to try to connect and then it fails and goes back to the Roku home screen. The PC shows "Couldn't Connect". Sometimes nothing pops up and all, but still the PC shows, "Couldn't Connect."
Is there some secret handshake?
Edition Windows 10 Pro Version 22H2 Installed on 9/9/2020 OS build 19045.2364 Experience Windows Feature Experience Pack 120.2212.4190.0