This subject may have been covered already but.....
Today I fitted roof bars to my MY13 Grand Cherokee. While I didn't need to I removed the factory rails to have a look under them. I was quite surprised by the amount of dirt under them. I cleaned the roof, and liberally waxed the surface under the rails. The screws were starting to show some mild rust developing so I cleaned them and applied some CRC Soft Seal and put it all back together.
I would think that this needs to be added to a yearly maintenance list.