It’s always weird when someone comes into a room with older students on an unplanned basis. I was on both ends of this during my college years.
I spent the first semester of my junior year on an internship in New York, and when I came back I was placed into a suite with two sophomores I had never met, taking the place of their friends who had just been suspended for a year for disciplinary violations in a process many felt was unfair and excessive. So it was a little frosty in there, to say the least. Over time, I became friends with one of my new roommates, and we are still friends today. But the other roommate and I never clicked at all, even though the two of them were reasonably close. That one and I were civil to one another, but that was about it; you could probably fit everything we said to one another over the course of four months on a 30-minute dictation tape.
The next year, I was part of a group sharing a great four-bedroom suite available only to seniors. We were really close friends who had all been in the same entryway as freshmen. Two of us (not including me) had been roommates since the first day of college, and three of us (including me) had been roommates as sophomores. In between the housing lottery and the beginning of the next school year one of us had a series of schizophrenic breaks, was hospitalized three times, and was both seriously medicated and seriously weird, and another of us – this was the pair who had continuously roomed together – became quite depressed over dealing with his friend’s mental illness, and decided to stop out of college for a year, living nearby and working in a call center. The schizophrenic guy returned to college at the start of the year, so he was occupying one of the bedrooms, and a sophomore transfer student who was an athletic recruit from a big-time college basketball program (and also a devout Catholic) was placed in our other bedroom – the one everyone else had to walk through to get to their own rooms.
I can only imagine his early letters home: Dear Mom and Dad, I am living with a mentally ill person who keeps talking about the voices he is hearing and two other guys who are super-intense academically and probably think I’m dumb. They don’t care about sports; they listen to punk rock; they drink, and I think one does drugs; they talk about abortion rights and female priests. Get me out of here! He was very, very sweet. Over time, we came to appreciate him, but he was always to some extent an interloper, and it was never a close relationship.
That said, what the OP describes is off the charts for anti-social behavior. The RA can probably help improve things a notch or two. But these guys are pretty much violating universal social rules for welcoming strangers; it’s hard to believe they are engaged in unintentional snubbing. I wouldn’t expect a whole lot.