I'm pretty sure there is. My 2012 Roo 19 had one.
Trying to find it is the trick. Sometimes they hide them very well. It could very well be behind one of those thin panels they like to put in to "hide" stuff.
On the other hand, since the unit is used, the previous owner may have removed it. Lots of threads on the forum here about the filters breaking and flooding the camper, so many folks have removed them.
1988 Coleman Sequoia - popup (1987-2007)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10