Went to college solo but was handed 2 roommates that I have to control?!

Did you join a dorm? You’re automatically in control if they were there before you joined.
Easy fix tho: testingcheats true and shift click on the sims you don’t want to control and click remove from household. That’s it

I've admittedly only sent my Sims to live in a dorm once and off-campus housing with roommates once, but the roommates in both situations were non-controllable. Is this a recent change?

You've probably joined the premade student household)

That happened to me once when I wanted to send a solo Sim to university. Kept forgetting Drake Hall in Britchester was the empty one and the other dorms were the friends premades.

If I remember correctly you can just move out the best of friends household and move your Sim into the empty dorms. After a while Julia and Becca just showed up as regular roommates in my game.

ive had my sim join a premade college dorm before and never had to control the other sims?

I know a lot about this game but nothing about living on campus.

I have never had a Sim live on campus. They always attend college from home because of all the stories I read about and saw on YT. My Sims are never late and my Sims don't get bad grades. There is no benefit from living on campus that I know of other than having the experience of dorm life as a player. I already did it in real life and don't need my Sims to do it for me. I don't think I am missing anything but want a full game experience. I just don't want to leave my other Sims behind unattended.

So, if I wanted to start a new save with a single young adult how would they even live on campus? They have to own property before going to college. After creating a Sim they have to live somewhere first so they can apply. I never figured out how to live on campus with a single Sim in a new save.

Can I create a student in CAS that goes directly to college? If so how?

no your sim would have to live elsewhere (unless they wanted to stay in a available lot in Britechester that isn't a dorm) then apply for university - they would have to wait 2-3 days for a reply then choose what degree/uni etc, and then they will have the choice to stay where they are, or move into dorms etc