Had a Heating Co. check my furnace. They found heat exchange cracked at heat exhange-burner entry venturi point and main center roll out missing. They said we should replace. Does that sound correct? Is the furnace safe to run?

They found heat exchange cracked at heat exhange-burner entry venturi point

Any crack in the heat exchanger is bad news and the furnace is not safe to operate.

main center roll out missing.

How come it is missing? Did someone remove it?

I would probably get a second opinion before I would let them condem the furnace.

Do not operate furnace until you get a second opinion and the furnace is fixed (heat exchanger replaced) or the furnace replaced.