Generic casting from chrome (where the PC sends the copy) has never been supported on roku. You need a chromecast device or android TV to receive that. Some applications use a somewhat different protocol where the PC/app tells the roku app what content to play and it gets its own copy directly. This should work with YouTube, Netflix, Plex, and perhaps a few other applications. For these cases you should see the 'cast' icon in the pc/phone app screen - you don't need 'cast' from the chrome menu.
Download an android emulator to your windows ex: NoxPlayer
Install app like web video caster on the emulator ex: Web Video Caster
Use the app within the emulator to cast your videos to your Roku
Exactly. Chrome dropped support to push you to Chrome Cast. Just another grab for cash and control on how you use your devices. Switch to Bing or any other browser. I did.....