In Harry Potter, the Room of Requirement is said to be able to give anyone anything they needed. Hence the name. Can the Room of Requirement bring another person, if the person inside it needed them? Or would it just make a fake cardboard or realistic copy of the person needed?
It can provide access to people, but cannot actually create sentient beings.
In the seventh book, Dumbledore's Army uses the Room of Requirement as their base. When they need things it can't supply, such as food, it opens up a tunnel to the Hog's Head in Hogsmeade; Aberforth then keeps them supplied with anything the Room can't provide.
“It’s quite straightforward, really,” said Neville modestly. “I’d been in here about a day and a half, and getting really hungry, and wishing I could get something to eat, and that’s when the passage to Hog’s Head opened up. I went through it and met Aberforth. He’s been providing us with food, because for some reason, that’s the one thing the room doesn’t really do.”
“Yeah, well, food’s one of the five exceptions to Gamp’s Law of Elemental Transfiguration,” said Ron to general astonishment.
This implies that the Room is bound by the same rules as other conjurations, the five exceptions to Gamp's Law. One of those exceptions is food; another is widely held to be sentient beings. (This hasn't been confirmed by JKR directly, but the books mention several times that no magic can bring back the dead, and magically-created Inferi are less useful than Death Eaters specifically because they can't think for themselves. If Voldemort could create sentient, perfectly-loyal servants out of thin air, he presumably would have done so.)
The other exceptions are speculated to be money, love, and one other thing, so presumably the Room can't produce any of these either—though they seem less likely to be requested.