When the burner flames blows back into the ignition compartment the roll out switch shuts the furnace down . If your rollout switch is tripped you probably have a stopped up heat exchanger (exhaust air is blocked) or a leaking heat exchanger (cracked). You can check the outside exhaust, sometimes it can be clogged by ice. I would recommend calling in a service technician to find out why the rollout switch tripped. Never by pass that switch, it is a safety devise. Good luck!
