Unless the equipment (car wash) malfunctioned, and fell off it's tracks, or spun out of control, or went down too far, due to a bad sensor, or it slammed into your roof rack, they will not be held responsible for the damage.....
Who is to say the roof rack was not on it's way out to begin with, who's to say if you strapped something to it, went on the highway and your cargo flew off including your rack because it was faulty, or broken or stressed or what ever......
I had the misfortune of a car damaged from a car wash, but they covered the cost of a new paint job on the car, why, well because it was their equipment that fell apart, had a metal clamp that broke, and when the drying unit came down, the metal clamp scratched the car from hood to trunk, a nice long racing stripe it made the full length of the car, I could not stop the car, I honked the horn the second I saw what was going on, but this being at the end of the wash, unfortunately the attendant did not hear this.
Once out of the wash I parked, brought over the attendant, and he got the manager that was fortunately onsite, they saw the damage and saw the cause, they closed down the wash for repairs and, covered my expense for a paint job......
I was lucky as it was their equipment that failed and caused the damage, unless you can prove the same, you will more than likely not get anywhere with them covering the damage.......this is why they post the disclaimer/warning
.