We've always had roof mounted systems - usually Atera bars (we generally get 50-60% of their value back by selling them on when we change cars.
We're trying Cruz's cheap bars this time, and they're ok, although the fitting system isn't as nice as Atera's.
We had Cruz Bici carriers initially, which are quite agricultural, but cheap, and not half bad, I have to admit. I recently bought a Thule Freeride for my bike, and whilst it's about 3x the cost, the difference in quality is very apparent - the Thule is easier to fit, locks to your roofbars and is easier to secure a bike to. I've used hired Atera Giro carriers, and while they're ok, I prefer the Thule Freeride, personally .
We've also used the bars for a roofbox - even on our Corsa, a long medium box fits alongside the freeride nicely. To lift the bikes onto the roof, we used to carry a small set of steps in the boot.
Whilst a towbar rack is appealing, we don't have a need to tow anything, and the recurrent cost is higher than replacing car specific roofbars with each vehicle change.