GE Supreme Silicone Sealant for sealing around roof vent

Dicor is definitely what you want for rubber roof use. I have used both self-leveling and the regular. I personally like the regular when sealing around roof vents, antennas and anything with a flange on the roof. And of course on vertical surfaces. It lets you build a bead between the roof and the flange.

The self-leveling is great for use on areas where a flat finish is desired, like when patching leaks with eternal-bond tape.