I was a Resident Assistant for a few years. We would ALWAYS make an effort to go say hello to anyone without a roomate the first day and we would make an effort ot introduce them around. We never wanted ANYONE to feel afraid and alone and well, its a scary first night away from home. Here is my bit, no roomate is far better than a BAD first roommate!
Here is the advice we gave to everyone at the first floor meeting held the very first night in the dorm:
1. Say hello to everyone you meet, introduce yourself to your neighbors, the kid who sits next to you in class, the people you meet at the bus stop, the people that work at the front desk! Get used to saying hello, and be friendly. Make a few friends in EVERY class and exchange phone numbers/emails, if you get sick and miss class, you can exchange notes. Get to know who lives on your floor, and get to know people in your classes. This will make you feel like you belong. This is your home away from home, and your family away from your family. And most people will prop their door open while in their room, great way to meet neighbors passing by! Of course, then they have to be sure to pay attention to the personal safety lecture, lol. But people generally are much safer if they know their neighbors and people who do not belong on the floor can be spotted right away.
2. DO NOT go home the first 2 or 3 weekends,DO NOT GO HOME~!!!! Stay on campus, hang out with and make plans with your new friends! If you start going home every weekend, you will never adjust, and you will continue to go home very weekend until you drop out. Being around for the "non class" part is a big part of the experience. Meet new people, find new places to hang out, have a nice time. You have to live your life, and learn to take care of yourself.
3. The first few weeks are the most important, this is when EVERYONE is still IN THE SAME BOAT! Everyone is looking to make friends, so if you see someone who looks lonely, or super shy, please make an effort to invite them out or be their friend! After the first month or two, people sort of settle into their "groups" and you can still make friends after that of course, but it is a little harder. People are open to making friends much more in the start of the semester!
4. Make friends with an UPPERCLASSMAN on your floor! They have been through the first year, they will be a GREAT resource for you, and if you need help, ASK THEM or of course YOUR RA would LOVE to help you! When the upperclassman go to do homework and study, follow their example.
Statistically (at my school anyway) kids who lived in all freshman dorms or only had freshman friends, were far more likely to FAIL out because they party too much. My school had a party reputation and was a bigger school, so parents don't worry so much about this if its a smaller school. The kids just learned bad habits, with no upperclassman to show them the ropes.
5. If they are still having trouble making friends, have them join a club or group. I used to recommend the outdoor club, they did a lot of hiking picnics, skydiving etc. Very friendly people! But most schools offer drama clubs, theater groups, music groups, political groups, student government, ballroom dancing etc etc. There really is something out there for everyone!
To the OP- I promise there will be people at the school there to look after your son, to make sure he is not alone. The school wants him to be successful and there are a lot of dorm resources to help students along in the start. Go say hi to the RA on his floor. You will feel better after I am sure!