I am baffled by why, when I bump down the temperature setting (when heater is running) on the thermostat that the roll-out switch trips, but does just fine if I leave the switch alone. My thinking is that there should be no difference. Lowering the temperature setting should the same as if the inside temperature got to the target and the unit shuts down normally.
Have someone else shut off the thermostat whyle you are viewing the burner area. If you dont get any flame rollout your switch may be bad. If you do, you have a flue or combustion supply problem. Be sure you have proper combustion supply air vents to the furnace room, if you have a combustion blower check to see if it needs oil and check the amperage with the rated amperage to see if it needs replacement. If it is an atmospheric, check the draft hood with a match to check draft.