I am actually in the process of removing my roof rails so I can have my roof repainted. I have large rust bubbles at the front of both rails. The rails are bolted to the roof from below so you will need to remove the headliner to get to them. Problem with that is that most of the rest of the interior needs to come out before you can get to the headliner. I almost had the headliner removed before I moved a couple of months ago, and since then the VX has just been sitting in the garage. I have an extra set of roof rails that I could take pictures of if it will help you.
I don't know how they are sealed to the roof, but apparently whatever it is breaks down over time because you are having a leak issue and I am having a rust issue. In looking at the rails on the VX the seal looks like some kind of foam, but I'll let you know if I get my roof rails off before you do.
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless