We just ordered a 3029W Windjammer with almost the same floor plan as yours. We ordered the optional fan in the kitchen area to assist in exhausting odors etc. because our stove vent does not exhaust outside.
If I were you I would remove the ceiling vent bracket in the kitchen and look for the wiring. It may already be there because your trailer could have been ordered with that vent fan option.
Rockwoods are difficult to fish wiring in the walls or ceilings due to the fact they have solid foam insulation there.
As a last resort you may want to try this type of wiring channel so that at least it cosmetically looks good. Click here:
Wire channelHappy trails,