By combining the two answers above you can see "it depends." Regular RV furnaces don't have an electric only option. As mentioned above, in the furnace the propane provides the heat, and 12V runs the blower.
Unless your roof air unit has a heat strip option, or is a heat pump, you won't have an electric only option. This is not uncommon, so what a lot of people do is use portable electric heaters. If you do a search on portable heaters you'll find a ton of opinions on what works best.
The big caveat is what Old Biscuit mentioned, and that's making sure your wet bay has some heat in freezing temps. RV furnaces will send some warm air to the tank area to keep your water from freezing. If you use space heaters this won't happen, so you need some way to keep the water tank and lines from freezing. I use a small, low wattage personal heater I picked up at Walmart. https://www.lasko.com/products/my-he...ter-white-101/
It's important to note that in my case, I have an area I can place this heater where it's safe, and provides heat the the proper place.
If your air conditioner has the heat strip option, be aware they don't produce a lot of heat, so if it's really cold, you may need to supplement. Similar with heat pumps, they only work above a certain ambient temperature.
Of course the all electric options only work if you have utilities.
Is there a reason you don't want to use propane?