Does your roommate know they have appliances built specifically for drying clothes? It's literally called a dryer. Even if he doesn't want to do that, hang them up and let them air dry. Using the ventilation ducts could be potentially dangerous, especially if he's storing them in there.

Well on a plus side, you got an excuse to give your house a massive spring clean..

He was trying to air them out.

i prefer the ceiling fan. i like to air dry my clothes

I had a roommate who'd hide scented candles in our ducts. It was fine until the candle heated up the duct and when he went to take it out, he gave himself second degree burns

Throw out all his socks haha

Hopefully you'll be able to get rid of that smell quickly, and that your roommate will think twice about how to dry their socks.

Sounds like he's got one concept down: drying. You should probably introduce him to another: washing!

I would beat the crap of your roommate. Or maybe hide dog shit it his room

I'm hopeful but also doubtful that this would mean they're wet from being washed.. but that is likely not the case. Gross