It isn't easy to say without looking at it, however, it easy for you to determine exactly what you have:
To determine what type of rubber roof is on your RVů
Easiest way; pull the trim ring on one of your roof vents and look at a piece of the roof material that is folded back from installation. If:
Both sides of the material is white or off-white, it is TPO.
One side is white or off-white and the other is black or dark gray, it EPDM.
Once you know then you can make your selection of sealing of products and know exactly what to get for the job without a WAG.
If your roofing is EPDM, indicated by a colored top and black bottom, you can use Dicor Lap Sealant.
If you determine that you have TPO and it has a fleece backing then regular Dicor Lap Sealant will probably be the right choice.
But if your TPO does not have fleece backing then Dicor Ultra Sealant System should be used.
Hope this helps!