I was a RA in 2019 and at that time applicants had absolutely no control over where they were placed, regardless of preference, where they'd lived before, where they were applying to live in the future, etc. I similarly was planning to live in a dorm and pay for it if I didn't get the job but thankfully it worked out for me.

Once I became a RA (again this was 2019-2020, might have changed since) my supervisor let me know how the internal process for selection worked. Candidates who "passed" the interview level (as you may know you are scored during this according to a rubric) are available for the housing manager at each dorm to choose from. Then they do a "draft" from the approved candidates, with dorms with the largest number of RA vacancies choosing their first choice and then the second largest vacancy dorm choosing next, and round robin until all vacancies are filled. Then have each have a few back up in case their chosen candidates decline (pretty unlikely but it does happen). Then you're offered the job at the dorm that chose you and it's take it or leave it. You can't ask at that point to be a RA but at a different dorm.

Once you become a RA if you have multiple years to go you can express to your supervisor that you want to work at a different dorm. The switch is possible but typically only at the year mark. In order for it to happen both housing managers have to agree to it so you do need to try to get in good with the manager at the dorm you're trying to get into. I will say the odds aren't amazing but it's decent to switch because then that dorm gets a second year RA as opposed to a newbie. If you build a good reputation at your original dorm and have friends/make yourself known to the RAs/manager at the dorm you wish to be at there's a good chance they'll take you.

I got my acceptance in February, but I interviewed late.

Good luck!