I have 4 Roku TVs and after the Airplay update all work great except the one that has HDMI CEC sound bar. I can get audio but I can’t control the volume from my phone in this particular TV. Every other TV behaves as expected (they are all on the same network too). I can control volume using the Roku remote both in Airplay and all other channels on this TV
Is the soundbar that you are connecting to your Roku TV a Roku Soundbar? Please be aware that if you are connecting an audio device to your TV, that you may be unable to control your TV volume since your soundbar may be controlling your audio when connected through HDMI CEC.
Please keep us posted and we will continue to assist you further.
Re: Airplay volume control on hdmi cec not working
For some reason the Roku doesn't support volume control via CEC with Homekit, which seems like a strange oversight. You can use Homekit and CEC to turn the TV power on and off and you can use the volume buttons on your Roku remote to control the volume via CEC, but the combination of Homekit and CEC volume control doesn't work. I gather volume control via Homekit only works with Roku TVs.