Flattest, warmest route to Las Vegas in January from NC

LuluL wrote:
We are new to RVing and are looking for the flattest, warmest route to Las Vegas in January from North Carolina. We don’t need the quickest route, but we are not dawdling either, just trying to avoid gas-guzzling hills and icy roads. We’re not ready to buy/subscribe to an app yet, as we will be working for a year before becoming full time RVers. Thanks for your help!