I'm unclear what you're trying to accomplish. Do you have multiple thermostats that can already control the boiler, or are you trying to control multiple radiators with the status of all thermostats (which also makes no sense to me).
If you have dumb thermostats which you can somehow get the temp from and nothing else, or you are using multiple temp sensors around the house to simulate remote thermostat sensors to control a central thermostat, then use the Thermostat Controller app. Documentation hasn't been added for it yet, but there's a post on how it works.
You can add multiple sensors to control a single virtual thermostat. That could then toggle heat on or off with a simple rule if your heating only has on/off control.
