Normally in your Roadtrek you only have 2 wires that goes to your heater. You mention a red and a white. The thermostat simply connect those 2 wires together in order to start the heater. It act like a single pole On-Off switch.
Your new thermostat has a diagram showing the terminal that must be used when you have 2 wires. (At terminal marked W and RH it doesn't matter where you put the red and the white as long as you use the W and RH. Leave the jumper as it is between the RC and RH terminals. The transformer on the diagram is not there and not needed.
see pic below