Ok, Two ways to do this.. Easy and complex.
First. to be sure you need at least 3000 watts of generator, A Yahama EF-3600i is ideal, or a pair of Yahama or Honda 2000 watt units with parallel kit.
Simply plug into the 30 amp outlet if needed use the proper adapter.. That's all folks.. Job done (One A/C) 5500 watts if you have 2 A/C's.
The complex way.
Find the power line to the A/C.. note on some RV's there may be devices between the circuit breaker and the A/C.. you want the last length of wire to the Roof.
Disconnect at the lower end and run a new 12 ga line with and outlet on the end of it to the point you just unhooked from, Hook it up, the outlet needs to be in a place you can access from outside.
A 2nd length of 12ga (I used two halves of an extension cord) runs from the end of the wire (use a proper junction box. LEVER NUTS (tm) or solder work better than wire nuts) and this line has a plug.
Normal operation Plug plug into outlet.. the circuit is now exactly what it was when the RV left the factory.
Generator running A/C only: Pull plug and using a 12GA cord (I really like the ones Sears and K-Mart sell with the push button on the outlet) extend to the generator, again you need over 2,000 watts, a Yahama EF 2400i MIGHT do the job.