DD is a freshman at a large school (55K) and she found her room mate through the Facebook page (we joked it was like Tinder for roommates). They chatted a lot online, then Facetimed and then she and I drove up and had lunch/spent the afternoon with her roommates family (we are about 2 hours from them). It was great, and they even said if they didn't feel it was going to work it was ok after the meet to decide not too live together. Our families get along great, both younger brothers play travel hockey and we are all Blackhawk and Cubs fans. We coordinated a lot (had a parent/kid group chat for supplies for the room), went for lunch together at move in and have done a few other social things together. Girls tend to use the Facebook route, I have also heard that some kids use Discord.
I cringe when I see mom's looking for roommates for their kid. DD did all of her applications herself and pretty much took care of everything, would send me the info I needed to input etc. A few boys I know just left it to chance and it's been fine. Our dorms have a lottery to actually pick your dorm (except if you are in a LLC and they get specific dorms), DD and her roommate prioritized A/C and location and are fine with their dorm (not the newest but it's in the "six pack" so they are happy but both moving into an apt next year (so much cheaper but they had to start looking in October for a place).