Keep in mind that the material that acts as a gasket or seal between roof panels, and between the top of the windshield header and the front roof panel, is not really rubber. It's some sort of flexible vinyl or plastic that is bendable and somewhat compressible, but less "squishy" than rubber or neoprene. For some reason I seem to think that all that is required on these is just keeping them clean with a damp cloth. (But I could be wrong.) On the other hand, the seals around the side windows, along the top edges of the windows, as well as between the main door windows and the little side windows behind the doors, are a more typical rubber.
For the poster above, I wouldn't put WD-40 on any of the seals. I'm not sure what the right thing to use is, but WD-40 seems like it might harm the seal material (at least that would be my concern).
I know that VW has a specific seal treatment product that they recommend for their Eos model's roof and window seals. But most of the discussion about the VW seal treatment was in reference to stopping water leaks!
I've never seen any mention of a specific treatment or dressing product for the C70 roof seals, but perhaps there is one.