I tore a triangle area in my roof and use Eternabond. It is a thin tape and it also turned up on the edges as indicated by Westwind. I went back to the RV store and found a 6" Dicor tape that was thicker than the Eternabond. It also was more adhesive and stuck much better to the rubber roof.
The tear on the roof...
Another view of the tear.
The patches.
The wide one is a Dicor Tape.
The narrow one is Eternabond.
FWIW
That's what I did.. Still holding.
BC