We were invaded recently as well. DW noticed some white powder near the slide. It turned out to be styrofoam dust. The ants had gotten in a tiny gap in the roof where some Eternabond tape wasn't completely secure and the P.O. had used silicone to make a patch between the coach and the end-cap. Honestly, silicone is good for almost nothing in my opinion.
I knew we had a small water leak around the A/C gasket (which turned out to be a small tear in the EPDM). I think the ants were attracted to the moisture in the roof.
To deal with the water, I re-sealed the entire roof including a new A/C gasket, fresh Dicor roof coating and fresh lap sealant.
To deal with the ants I pried off some of the wall panel and even drilled a few holes above the dinette slide. I sprayed Raid in the holes and then ant-bombed. Right now there are Terro traps finishing up any stragglers. A handful of poisoned ants staggered out of the roof vent ALLLLLL the way back in the bathroom. I removed the skylight and sprayed in there as well. Stuck a few RAID traps in there for good measure.
Normally I might not bomb such a small space but we are re-painting, re-flooring and re-carpeting the whole space. And, honestly, I'm willing to do whatever must be done to get rid of the ants. Once they establish a colony in the styrofoam, they can wreak all kinds of havoc including ruining the A/C ductwork. If that happens, your A/C is just venting into the roof.
Anwhoozle, I haven't seen any ants for a few days. Fingers crossed, right?
Good luck.
edited to correct poor typing