I have a boyfriend. But my roommate introduced a guy to me the other day, and he asked my phone number. My roommate already knew I am in a relationship, but she said she just wanted me to have one more friend. She knows my boyfriend and I are in a long distance now, and we see each other monthly. The guy she introduced to me is one of her best friends.
But since yesterday, he texted me very late at night. And he asked me whether he could come over and be my company. At the time I received the message, it was about midnight. I told him it was a little late.
Should I stop texting the guy? Honestly, I am lonely without seeing my boyfriend often. But I don't know whether it will lead to cheating.

You don't know whether it will lead to cheating? Really? Do you have no will power? Do you love this boyfriend? If you do, you will keep this new friend as a new friend and that's it. Coming over late at night is not acceptable. He needs to know that you are committed to your boyfriend and that nothing will happen with him. If you really don't trust yourself with this boy, then no, don't text him back.

And this is why me and my (ex)girlfriend will never work out...

Men try to act like they don't care when they know you have a man but no it not the right decision. I mean what dose he have to come over so late, you got to look at it lik this if your man was in the same position how would you feel? And most long distance relationships are not easy.

If you're not sure if it would lead to cheating, then you aren't as attached to your boyfriend as you say you are. You need to re evaluate your relationship first, and no, he should not be texting you if he's going to try that midnight madness game.

You should keep things within the boundaries of good behavior, and let him know that calling that late looking for some face time, is unacceptable and disrespectful.

Yes, stop texting him, no matter whose friend he is. It is only encouraging him to think he has a chance, since he probably sees you as lonely, and in need of some man intervention, into your boring life.

Whether this is true, or not, is irrelevant, but that's the way your friend sees you, and why she steered this dude your way.

If he's doing that he's creepie.
If this carrys on for ages, he's stalking you and you have the right to call the police, (By ages I mean years)
TELL HIM TO SHOVE OFF! lol