Not an electrician, but here's what I have experienced/learned:
Romex in conduit has to be derated. Something about the insulation and the conduit not allowing for enough heat dissipation. THHN wiring is a better bet for 120VAC stuff.
Low voltage wire in approved conduit (smurf tube, orange tube, and pvc are approved) does not need to be CL2/3 rated. I am not sure if that rule only applies in the same room for fire reasons. The worry is that if an unrated wire goes between rooms and a fire breaks out, the insulation in the wire can act as a fuse and carry the fire all around the house.
However, if you are worried for code/permit reasons, it can all vary by jurisdiction and the inspector you get.