These students work for ResEd and are assigned to each residence hall floor. They enforce college policy while carrying out hall meetings on topics such as gendered/non-gendered bathrooms. An analogous (but not equivalent) position in OSCA's housing co-ops is Housing Loose Ends Coordinator.
They get singles and have some say in what dorm they live in.
RAs will tend to report you for drinking, smoking reefer, having too many people in a room or for other violations.
RAs take their jobs for various reasons, ranging from to a desire to enforce rules to a desire to subjugate them to saving money on housing. As such, they approach their job in a variety of ways. Know what to expect from each one and don't be afraid to approach them with issues. At the same time, know how to avoid them when necessary.
Back when ResEd was still ResLife, RAs were called RCs, for "Resident Coordinator." This term was abandoned, possibly when it was realized how difficult it is to coordinate residents.
There are two types of RAs. About 75% of RAs are cool and just took the job because they needed the money and wanted a bigger room. Make friends with this type and you'll never get written up as long as you aren't an asshole. 25% of RAs are the insane power-tripping type who think that because the school has given them the ability to file paperwork, they're the campus police. These tend to get placed in freshmen dorms. There is no reasoning with this type. You are inferior to them, and they must demonstrate it by getting you in trouble as much as possible, or they will feel like they're losing their power. The best course of action with this type is to cause as much trouble as possible without getting caught, and to ignore them when they talk to you in order to undermine whatever authority they believe they have. This will break them.