Just because both are based on Linux has nothing to do with Chromecast. Chromecast is basically a proprietary protocol of Google and requires the proper support on both devices. True Chromecast support probably involves some $$$ licensing fees. There are various 3rd party types of casting, all slightly different and some may have also have license fees.
I have a Moto G5+, and the only casting I can do is either with the You Tube app to You Tube on the Roku, or audio to my AV receiver, which supports audio-only Chromecast.
One major distinction is that mirroring consumes two screens. Mirroring means whatever is on one screen is showing on the second screen, therefore you can't use the first screen to do other things without interrupting the second screen. Casting does not do this. I can cast something to a second screen and then do something entirely different on my phone and the second screen will still play what's been cast without continuing to use my phone's resources.
Wrong! What you mean is your phone's casting capabilities are limited.
I have a PC with multiple monitors. I can use Chrome Cast Tab to Chromecast on one monitor full screen and run on the other monitor other computer applications at the same exact time while the monitor contents are being cast. I do it all the time. So I just proved Chrome Cast Tab is exactly the same as mirroring one computer screen.
TheTick (aka "Moose Twit" affectionately called by chht) Roku 3 for Pokémon TV / YouTube / Animal Planet GO / HBO GO. Chromecast for most other media because Roku Mirroring sucks , how many clicks in Wndows 10 (about a dozen) to Miracast on Roku vs 2 with Chromecast. Verizon FIOS TV and Internet Service
Roku needs to justify why they support Apple's proprietary Airplay, but not Google's proprietary Chromecast. Especially since Apple's IOS has only a small fraction of Google's Android/Chrome.
I can understand only supporting a spec which makes a serious attempt to be universal (e.g. Miracast), but Roku isn't doing that, they're supporting vendor specific solutions. How much is Apple paying them?
I tried using chromecast with my macbook pro and Roku, and it does not work. However, apple products support apple's airplay, a version of screen mirroring.
But it's actually more advantageous than chromecast, which is limited to mirroring chrome browser windows. Airplay mirrors any screen display on my mac. PLUS, I have the option of screen mirroring to my tv OR "extend desktop."
But Airplay requires the roku streamer to make this work. It's great to have access to a large tv screen for my laptop.
Chrome also offers the choice to cast the whole desktop or a file, not just a tab to a chromecast device or android TV. But, it can't extend the screen and I think on a Mac it may not be able to send audio when mirroring the whole desktop.
One major distinction is that mirroring consumes two screens. Mirroring means whatever is on one screen is showing on the second screen, therefore you can't use the first screen to do other things without interrupting the second screen. Casting does not do this.
I have a PC with multiple monitors. I can use Chrome Cast Tab to Chromecast on one monitor full screen and run on the other monitor other computer applications at the same exact time while the monitor contents are being cast.
Like he said, “Mirroring” uses two screens. The screen being mirrored, and the screen it is being mirrored onto. Your setup has three screens, of which two with identical content, are taking part in the mirroring.
The local source content on one screen is being streamed from that local screen to also appear on another screen. If the local source content changes, or if the device is powered down, then either the content of the other screen changes also, or the mirroring halts.
“Casting” takes the remote source of one screen, ‘casting’ the content from that remote source, to another screen, leaving the original screen free to do whatever one wants. The other screen continues to display that remote source. With your setup, “casting” will leave you three screens with independent contents. The device which originally had the content can even be powered down, and the screen which received the cast, will still display the cast.