Is this guy on the lease? If he’s living or “staying” there, he should be on the lease. If you and your roommate are not willing to re-negotiate the lease, then there really is nothing else to talk about.

How you discuss this with your roommate is to state that you do not want him there. That is completely honest and sensitive. If she can’t handle it, offer her a glass of water.

It seems to me insensitive is already present, and sacked out on your couch. He needs to go. You should not have to feel invaded.
Sit down with them and tell them, right now, this cannot be, he needs to get himself somewhere else. How many names are on the lease? Not his? Bye bye.

The 3 of you know one another. The fella is the odd man out, and everybody knows it. The 3 of you MUST talk, and it obviously falls on YOU to seize the initiative. Do it NOW, and be firm. This is disrupting both you and your roommate with implications for your educations. Set a deadline, and in the meantime state unequivocally that if he must sleep at your place even temporarily, it must be when you aren’t around.

It’s a problem worth discussing. It’s your friend’s and your place. He’s in your way—you’re not in his way.
Discuss it with a positive attitude to avoid much conflict. Ask how long he is planning on staying, and if she says anything less than “he’s leaving tomorrow”, say that you are not comfortable with it and it is not in your (“our”) agreement.

I think you need to formally schedule a talk with your roommate about him. You can schedule it over dinner or over pizza, or over a latte or over a beer. But make it a time specifically to talk, not just some random time when you are passing by in the kitchen.

And, re-emphasize with her that it is because of your dependence on your parents that you need to set this up. And then ask how the two of you can work together to get him out and when.

I think you might want to talk to your folks. They could probably find you another place to live, or go to bat for you with the landlord.
And it would reassure them to know that you take their expectations seriously.

There’s no way to make this conversation less awkward than it will be. You just have to do it, like ripping off a Band-Aid. She may react reasonably, she may not. This is just how it goes in roommate situations, especially when you’re all young and figuring out how to behave with each other. For each of you, there’s a trade-off between what you want and what you can reasonably ask of another person, and at this point in life, not all of you are going to figure out the balance correctly.

Whatever happens, you should also tell your parents as soon as possible. They are going to figure it out anyway, so you may as well get ahead of that. If they truly won’t accept the situation, then at the very least, they’ll have to make alternate babysitting arrangements. It’s not fair to them to spring this on them at the last minute. If you’re very lucky, they’ll help you move into a different living situation. It might be different if you were welcoming the guy into your living room, but the fact is, you are as unhappy about it as they will be. There is no reason for you to “cover” for anyone.

And whatever you may believe about “really liking the relationship that you have with your roommate”, the fact is that she isn’t respecting you. You told her how you feel about dude sleeping over, and she’s ignoring that. This tension, plus the fact that you feel uncomfortable in your own home, make the situation unsustainable. Something needs to change.

Sit down with both of them: “Hey guys, I’m not sure what is going on here so I think we need to talk about it. Roomie asked if you could stay here for the semester and as I told her, that cannot happen. My parents pay for my portion of the rent and they would blow up if they knew a guy was staying here. So you need to leave now. I have no idea when my parents might drop in and I don’t want to have to explain to them why you are here.”

If you are uncomfortable with saying this, just think how uncomfortable he is making you feel in your own apartment that you pay rent on.

@Wine Nice to see you stayed after that last fiasco. :( Just frame the debate in a my parents won’t allow this, and they’re paying for a part of the apartment. If they stop, we’re out on our asses. He either leaves or you all leave.

Just explain the situation to your parents exactly as you have explained it here, and ask them to drop by when he’s likely to be camped out on the couch.

If you’re not willing to use that little ruse, take you roommate aside and tell here that if your parents drop by and the boy is obviously sleeping (as opposed to having fallen asleep), the spit is going to hit the fan.

If that doesn’t work for you, wait until you and the boy are alone, and ask him, directly, “How far are you from other arrangements? Can you afford the rent here, because if my parents drop in and you’re sleeping on the couch, I’ll likely not be living here.” Alternately, ask the roomie about your ½ of the rent.

If you want to be passive/aggressive, start spending inordinate amounts of time using the couch.

You could say, innocently, “Hey, roomie? I was wonderin? which ½ of the couch is mine?”

Ask a friend if they would mind spending a couple of nights sleeping on your couch. Beat him to it.

None of those work for you? Try the direct approach.
Or I can offer other options. :)

@ibstubro “If you want to be passive/aggressive”

Just no.

Options, @dappled_leaves. Options and personalities, relationships.

I do not disagree with you. :)

@Wine: Please let us know how things turn out.

@jca

Update: The day I posted this he approached me and explained his situation. Basically his dad purchased a new house with his step mom and didn’t manage his money well. This resulted in the family having to rent out most of the house to get by. He said he could pay part of rent and help out with groceries and I told him I would have to sleep on this because I wouldn’t feel comfortable with making a profit from lying to my parents. (Also if someone is going to be sleeping in the living room I wouldn’t want to have to tip toe around without some sort of compensation)

Later I was able to sit down with my roommate privately. I was originally torn with this ethical dilemma but mid conversation realized that there’s no way I could feel good about doing any of this without my parents permission. I told her the two main issues were that I didn’t want to upset the people paying for my college education and rent and it wouldn’t feel right for me to lie to them. I’ve never had a reason to lie to them before, and I feel lucky to have a close relationship with them. I didn’t want to risk losing their trust. She was sad for her friend, but I think she understood where I was coming from.

The next morning I got a call from my mom checking up on how I’ve been doing. I asked her if she was busy and if she could sit down because I wanted to tell her something. I explained the whole situation and she was willing to let him stay for the rest of the semester if I thought he wasn’t a bad guy, just someone having a hard time, and if he brought his own bedding. She was about to say yes and that she wanted to meet him first, but then remembered that my dad would need to approve of this too. My dad didn’t feel comfortable with a guy staying in the same apartment as me for a time period that long, so I told my roommates guest that he would have to leave within a week.

You are a pretty amazing young lady! Can I be your mom too?

You handled it beautifully!

Thanks for the update, @Wine. I think you handled it well and I think your parents made a good call.

And I hope you stay here on Fluther!