Sorry, but I was able to cast from my iPhone 7 to my Roku TV. Now by using this method, I am able to watch any video on my TV without age restriction; however, the original issue still persists, and I'd like to see a solution to it.
If you could provide the details on how you did that, it would be great information here. The only thing that is known to cast from an iOS device is by using the Roku app on the device, and that only permits casting music or video stored on the phone itself.
I don't have all the detail how I cast, say youtube videos, on my TCL 40" Roku Smart TV. However, this is what I followed:
Note: Roku does not technically support mirroring with any iOS device. However, you can screencast to your TV from several apps, or cast any media that is stored on your iPhone.
1. On my Roku TV, I went to Settings
2. Then, pick System
3. Under System, pick Advanced system settings; then, Device connect (Device connected)
4. Next, under System, pick Screen Mirroring
5. Go to "Screen Mirroring Mode" and select "Always allow"
6. Download, install a Roku app for Mirroring
Note: the iPhone and my Roku TV are both on the same WiFi network
7. Follow the instruction on the app, and find your Roku or Roku TV with the app to connect. One may have to fiddle with your app or TV until your Roku device or Roku TV shows to connect in the app.
Next, I went to, say Youtube, and clicked to the mirroring icon on Youtube to see it there. I tried to use it with my browser, but I am not able to do so. I guess it is because Roku does not have a browser, but I was told to try a different browser, not the Google Chrome. As of now, I have yet to experiment with another browser.
I hope this could help others here.