Depends on the A/C.. And I really do not care for them in any case.
Here is the solution.....
On one of my two A/C's there is an optional drain cup, this will fit on either of them but only one offers it as an option.. This is a cup with a drain hose fitting that basically attaches to the drip tray just under the drip lip.. (If you do not know what these terms mean remove the outer cover from the A/C and look, you should be able to figure it out in under 10 seconds)
The drip lip is where the water drips out of the tray.
From here you use a hose, which you can route to the drip down point of your choice.
The problem.. You now have this hose you have to attach to the roof. IF alge builds up in the hose (Happened at work with the big Lippert) you have a problem so you now have to clean it from time to time.
But the water goes where you route it.
Fact... My last trailer I had a window AC mounted in the front window, Actually worked rather well.
I put a funnel on the thing and drilled a hole so it dripped into the funnel, then used tubing to get it down past the LP tanks since I did not want it dripping on the tanks, worked well and was easy to clean if it clogged (only a few feet of tubing).
This would NOT work on the rooftop units as there is no room for the funnel, but the drip cup that Advent Air offers .. Does the same thing.