On a greater sense it depends on what company they're sorted into which is mostly "random" with some exceptions for band kids and some recruited athletes. Roommate pairing for the first two trimesters is typically random and for third tri I will ~hopefully~ be able to pick my own roommate.
Food and drink are allowed with obvious restrictions, no sweets or junk food and most classes don't earn caffeine back (it's a rate.) The class of 2025 earned caffeine back in like early September if I remember right. If you're smart you can find ways to sneak food through the mail, as long as it's not out then you can't get in trouble for it unless there's a special inspection (incredibly rare)
Extra pillows and stuff doesn't really happen haha, you can get one sent to you but I wouldn't simply because it takes up limited space and the pillow here is fine.
I sleep with my foot blanket and so does my roommate, folding it takes like two seconds. During indoc I know a lot of kids that slept with towels and I did for a few nights but ultimately you're so tired you'll fall asleep without a towel if you don't have one. Personally, I wouldn't pack a towel for indoc again, as it wasted space and didn't make much of an improvement on my life.
If your DS wants anyone to talk to before indoc just PM me and I would be happy to talk to him