I have a 2008 189FBR. The roof type on that is TPO (Thermoplastic Olefin). There should be a manual on it in the paperwork that came with the trailer. If you don't have that, e-mail or call Cruiser RV. I do it all the time and they get back to me within a day or two. The existing caulk will be difficult to remove fully, you may need a solvent. good luck.
2007 FJ cruiser
Tekonsha Prodigy Brake controller
Yamaha EF2400is generator