Roku tv

What model TV is your bedroom TV? Would that be the C157X, or a different model?

TCL Roku TVs (4-Series, 5-Series, 6-Series, 8-Series) should support AirPlay. List of AirPlay 2-enabled smart TVs - Apple.

Verify that AirPlay receiving capability is activated in the TV settings. It should have an On|Off setting.

You may need to add the TV to your Home setup, and assign it to named room. Add a HomeKit accessory to the Home app - Apple Support

I know your issue is about getting a code, but if the Roku device is not showing up there might be another easily fixable issue. If your Roku TV or Roku device is not showing up in Airplay or screen mirroring options, do this. Roku 10.5 software caused an issue with Airplay but can be worked around as follows:

On your Roku device home screen, go to Settings>System>Power>System Restart>Restart. After it finishes, (the TV will turn off, then on again and take 30 seconds or so to get back to the home screen) proceed as follows.

From the home screen on the Roku device go to Settings>Apple Airplay and HomeKit and select. It will reload the Airplay app (it took about 20 seconds on my Roku TV). Now turn on apple Airplay from that screen, (it is defaulted off with the reset). Now, when you go back to your apple device, the Roku device should show up as a screen mirroring or Airplay choice, assuming the devices are on the same network and they meet the other Airplay requirements. The first time you attempt to use it, it should provide a code. Whether or not you use a code every time, or just the first time, is an option you can choose in the Airplay settings on the Roku device