My visit was actually to the Mayen food truck location, which was in front of a REWE (a grocery…read moremarket chain). Unfortunately, I'm unsure what that food truck's schedule is. However, Westerwälder Hähnchenbraterei seems like a chain, and they have a website that shows various trucks' schedules and locations in Germany!
This food truck has whole chickens roasting inside, and you can see and smell (oh my god, just the aroma lures you to the truck) them. You can either purchase whole roasted chickens, or just parts. We ended up getting a pork sandwich. It didn't seem like they had a chicken version of the sandwich, otherwise I would have definitely tried that instead. The pork was soooo good though! It had a thick slice of pork (mostly meat, barely any fat) on toasted bread, with onions. Simple sandwich, but the pork was tender, and very well-flavored. I think it was less than 5€ for a sandwich, but the sandwich was pretty filling. All in all, you have to try it if you come across this food truck!
NOTE: CASH ONLY!