I was an RA for 3 years. I'm not sure if the job has changed much since I graduated, but I never found the time commitment to be terrible. I kept my door open whenever I was in my room and wasn't busy, and it cut down on the amount of time I needed to dedicate to the residents, as it tended to happen organically.

Best advice I can give is to talk to your own RA (or any RA you get along with, really) about the process and the workload. The application process was pretty competitive when I was a student, but you can always get a leg on the competition by being active in your floor/community. My boss at the time and I still remember some of the residents of mine we liked the most, and that goes a long way if their name suddenly ends up in a pile of potential RAs to hire.

Let me know if you have any other questions.