[landmannnn]

As you have found the paint is pretty thin on those channels and it does rust. No immediate concerns...

It looks like from your pictures that a previous owner has stuck a rubber profile in the channel, or perhaps it just looks like that.

 

[landmannnn]

There isn't anything underneath, but it is unlikely to rust right through.

 

[landmannnn]

Ok. The roof is all one piece with those roof channels just part of the panel. So no gap for the water to leak into the cab.

It does look like somebody has put a sponge seal along the channel, probably to cover the rust.

So I would just leave it alone for now and when the weather gets better pull out the rubber seal, rub it down and paint it up.

 

[landmannnn]

The wet headlining is something else. It is the foot of the roof rack.

If you look at the front of the front support at roof level there is a tiny weep hole, you might have to push the rubber down to see the hole. Normally it just gets blocked.

 

[landmannnn]

To be honest I'm not sure. I could have a look at mine when I get home early next week.