I share a place with a roommate, but something feels off. My roommate literally stays in their room all day, usually keeps the door locked, and orders food to eat in there. There’s zero responsibility for cleaning or shared spaces. I’m at a loss about what to do. Should I talk to them, or should everyone just mind their own business?
I think you should talk directly. Just say clearly, ‘we need to share the common area.’ If they still don’t respond, make a list of the responsibilities for rent and cleaning, and post it on their door. Sometimes an official tone can be effective.
It happened with my roommate too; he would eat in his room. That’s when I realized he had a bit of social anxiety. I had a coffee with him and asked in a relaxing way, it worked. It’s worth a try.
This is kind of strange, why would someone just hang out in their room all the time? Are they disconnected from their friends, or going through something bad? Maybe you could suggest a couple of activities to get them outside. Otherwise, it’s just boring 
Some men have this kind of escape mode. Maybe he’s bored with work, or perhaps he’s embarrassed about something personal. But you definitely need to remind him about cleanliness and shared space responsibility, or else he’ll think he can always get by with it.
Update: Actually, this situation has been going on for about 2 months. At first, I was gentle because I thought they were tired from work, but now I really start to feel uncomfortable. There is no effort to go out or talk.
Honey, this isn’t normal. No matter how old you are, you must know your responsibilities. If she were my daughter, she would talk like a person, and if she couldn’t find a solution, she would part ways. Everyone’s life is precious 
I went through the same thing; my roommate was like that when he was about to drop out of school. Turns out he had fallen into depression. Make sure to start a conversation and ask something like, ‘Is being this withdrawn causing you any trouble?’ The rest depends on how he responds.
I think he might be dealing with something else. Not leaving the room, even eating there… Either he’s texting someone or doing something secretive. Have you noticed if he’s on his phone a lot?
Cleaning and shared space cannot be confused with individual freedom. If you are the one using the shared space and also the one cleaning it, it means the power balance in this relationship is disrupted. This won’t work without a clear agreement with your friend.