There is a third type that could be on your roof.
I specifically asked my dealership what type of roof was on my 2019 High Country and they told me it was Alpha. They told me it is NOT EPDM or TPO and to NOT use products for EPDM or TPO on it. I needed to use only Alpha sealers and caulking. So, the day I purchased the camper, I picked up a couple tubes of Alpha calking from them. It's not cheap!
Before just assuming it's one or the other, I suggest you confer with your dealership and get a straight answer. If you do have the Alpha system, you do not want to be using anything but Alpha sealers on it.
Here's a link to the Alpha web site: Click here.
2019 Montana High Country 375FL
2014 Chevy Silverado Duramax, 6.6L Dually