Can not get the Roon display on to the Chromecast TV

I must just be a dummy. I installed Chromecast Ultra and am able to cast YouTube videos & Chrome tabs to the TV, both from my iPhone & from my Windows desktop. I set up the Roon Display tab and it shows the TV active. But I can not get the Roon display on to the TV at all. I also tried to use the Web display option on Chrome and I can only get a grey image with the word Roon on it. I have tried both with a Roon remote on my iPhone and with Roon remote on my Windows desktop. Remember that I can not access Roon core on my laptop because the screen is f-d up on it.

Help please.

I also

Never mind. I found a YouTube video that showed me to go to the display volume icon at bottom right to start the cast.