This is very common among depressed people. It doesn’t mean he isn’t depressed. Depression is easy to hide. These celebrities are a good illustration of that. 22 Celebrities Who Have Spoken Out About Their Depression
At any rate, I suggest you talk to your roommate. Can you ask him if he wants to talk? Is it possible you are being a bit insensitive to him? If you know his family well, maybe let a parent know that he seems to be struggling.