Good evening a HR92 is only needed on rooms where you want to treat them as specific zone with their own climate, and the ability to call for heat when the temp drops.
So for example a bathroom normally is set to a higher temp so you dont feel cold getting out of the shower in the morning and evening, but has a lower temp the rest of the day, a small office if used as a home office may need to be heated only monday to friday at 20 degress but weekdays 18 degrees.
If you didnt fit a HR92 (or similar) when the boiler came on it would heat up the room based on the TRV setting, however if the room (eg bathroom was 16 degrees) but all the other thermostats didnt call for heat the bathroom would remain cold as it had not way to signal to the boiler it needs heat.
I hope that helps clarify the situation, in summary any radiators which need to call for heat need a thermostat or HR90 installed, otherwise they will only heat up when the boiler runs and will switch off when the TRV value is achieved.
Good afternoon, I just wanted to follow up to see if you required any further assistance?