One of mine was a sock eater and did have to have surgery for an obstruction. They don't have to die a horrible death but it can be expensive to have the surgery. Knowing your dog has a fondness for socks, I'd prepare myself financially in case that happens, by building up an emergency savings fund and/or by signing up for some sort of pet insurance. Make sure the insurance you get would cover that sort of surgery. Labs are notorious for eating stuff they shouldn't so, in addition to trying to avoid the problem, you should be prepared in case the worst happens.
if he's still getting socks, you and your roommates need to be even more scrupulous about keeping them inaccessible. You already know that telling him to leave it only works if you're watching. This is seriously more a matter of training yourselves right now, more than training him. It's a huge pain, I know. I'm sure my dog did not associate his surgery with the act of eating the sock, so no deterrent there. He got at least 2, maybe 3 more socks after that. One I didn't know about until he puked it up in the middle of the night. The other he gulped down before I could get it away from him.
If you see him grab and eat a sock, you can give him hydrogen peroxide, which will cause him to vomit. You pretty much need to do that within 30 minutes or so. I'd check with your vet to determine how much to give a dog the size of yours and how long you have to give it if you see him gulp something. Members on here have had dogs eat socks, underwear, dish towels, rocks, sticks, balls, squeakers from toys, all manner of things. He might outgrow his fascination but I think you've got another year, probably more, before that happens.