I was hoping another Roadtrek owner would jump in here with an answer for you. I've searched around without any luck. You can try contacting Roadtrek for some help/replacement or at least find a dealer near you:
https://www.roadtrek.com/ You can download an owners manual there but there's noting on the window latches in it.
I'd try taking the phillips screws out to try to see more. I'm thinking you can unscrew the inside piece but can't figure out how you'd hold the outside piece while doing that. There's no sense taking the old on off till you can find a replacement. Then you'll be able to see how it's held together.
Don Ford
2004 Safari Trek 31SBD (F53/V10 20,500GVW)
'09 HHR 2LT or '97 Aerostar MiniVan (Remco driveshaft disconnect) for Towed vehicles
BlueOx Aventa II Towbar - ReadyBrake Inertia Brake System