I did some work in my laundry room today and it required shutting off the furnace. This evening I noticed the vents were blowing cold air. I checked the furnace and it was flashing 5x. The cover says that means "Roll out open". It's York...about 14 years old.

What do I do?

From a York service manual: Five Red Flashes - Rollout switch or auxiliary limit switch open. Check the rollout switch on the side of the burner box. It is a manual reset switch. To reset, push the small button in the center of the switch. If it cannot be reset or if the switch trips again, contact a qualified serviceman.

I found the manual here: http://www.yorkupg.com/PDFFiles/172988-UUM-C-0606.pdf

Good luck!

The roll out open means that the little sensor that is in front of the burners was tripped. It is a sensor that trips if the flame rolls out of the heat exchanger area. Some of these have little square buttons that can be pushed in to reset. Others look like a transistor that once tripped requires replacement.
Call your local gas supplier and they can fix it fast for you.