Rollout switch tripping

When it trips, does it fall down and go bum?

Seriously, a roll out switch is measuring a temperature that is higher than it should be at a location where it should not get that hot. Usually at a draft diverter or the burner vestibule. The conventional logic you might believe is that setting the thermostat at 62° causes the switch to trip. That is not the case. By setting the thermostat to 62° does not have anything to do with the overtemperature condition.

What may be happening is the boiler is off for a longer amount of time after you lower the temperature.  The burner runs at least once per hour when set at a constant temperature.  The burner will stay off for several hours overnight when you lower the thermostat.  This allows the chimney to get cold.  After several hours of down time that saved you on fuel, the burner lights and the cold chimney does not draft as well since it is colder than usual (if the burner was operated within the past hour).  This cold chimney causes the flue gas to overflow and spill out the draft hood or burner vestibule into the boiler room causing the higher temperature to trip the roll out switch.  

You need to inspect the chimney for problems with the draft.  Partially blocked chimney base.  Perhaps the chimney liner is failing.  or you could have some carbon build up inside the boiler itself. You need to look at the cause of the spilling flue gas and correct that.

@Saul , Rollout Switch, or Spill Switch? The Spill Switch is at the flue pipe.

Somebody needs to check the chimney immediately. You can't just keep resetting it. Its a safety device that's trying to save you but you won't let it. Is there a cap on the chimney?