Welcome Andy. The answer is maybe
Exposed tanks (fresh water & waste tanks) and exposed plumbing will freeze.
The Roadtrek brand of Class B's has this to say:
Is the water system designed for winter use?
In 190 and 210 models, we’ve added a second fresh water tank inside.By using RV anti-
freeze in the black and grey water tanks, the water system can be used in below freezing
conditions to 10 degrees F (-10 degrees C).In 170, RS and SS models, the fresh water
tank and lines and water heater should not be used in below freezing temperatures.
However, you can still use the sink and toilet by carrying a fresh water supply inside the
vehicle and using RV anti-freeze in the black and grey wastewater tanks.
Look for a Class B with an interior fresh water tank and minimal exposed plumbing.
Here's some specific Roadtrek plumbing info: link: viewtopic.php?f=9&t=29
Models from May 2003 onward are better suited for freeze / thaw conditions.
Roy's "Our water froze up last night" post is worth a read. Link: viewtopic.php?f=9&t=690
Let's hope other members have some info to share re: winter travel.