Do those gasoline lights need ballasts or do they run right off the motor?

Of course they need ballasts, the ballasts are powered by the generator which is powered by the engine.

good question, i belive they have ballasts also they are diesel

They're probably just regular AC MH floods but wired to the generator instead of connected to a service.

I think on these trailers they tend to be remote ballasts in the generator compartment, even with the regular floods since it reduces the weight at the top.

i wasn't sure if they just made the generator give the right current and voltage.

You can design an alternator that will drive a light directly, but it will be an expensive unit, and only applicable to a single lamp type. Cheaper and easier to make an alternator that will provide a low loss regulated AC output at some power, and use regular common magnetic or electronic ballasts to drive the light. As a bonus you get the ability to provide AC power for other uses as well.