It's not the running amperage that matters it the starting amperage. Also called locked rotor amps and inrush current. This is the amperage required to get the compressor moving from a dead stop. Even though this takes less than a second the power supply will need to be large enough to overcome the "locked rotor amps" LRA is usually 6-7x or more that of running amperage.
The 3000 watt generator should have no problem starting any rv roof unit.
As mentioned above you don't need a unit that big just for the air if you install a soft start cap. A 2000 watt generator will deliver 15 amps or so, more than the a/c needs. It may not be enough to get the unit started though without an upgrade to the start capacitor. We installed a micro-air in our new camper. They work great.
https://www.microair.net/products/easystart-364-3-ton-single-phase-soft-starter-for-air-conditioners