Can't speak much to the background of the making of the film, but I can give you my personal interpretation. (Possibly some vague spoilers.)
I take a pretty literal meaning to the character's names (well, other than Stalker himself). I think of the Stalker as someone with great belief of a spiritual (not necessarily religious) or artistic nature. His beliefs are not easily explained (or are, in fact, often contradicted) by scientific, logical, or deductive reasoning, represented by the Scientist and the Writer, both of whom have the ear of a rather large audience. The Stalker is convinced that if he could just bring the others to the room, they would have a moment of enlightenment and see things from his point of view. But of course, things are much more complicated than this. In a simplistic sense, this could be seen as just the old science vs. religion debate, and in lesser hands the film could have become tired and didactic. But I don't think the film has to even be about spirituality to work. It can simply relate to the human desire to share something that you love deeply, something that you consider to be an integral part of who you are, with others, putting yourself and your beliefs on the line and leaving yourself vulnerable to be seriously wounded. Because of course, if the Stalker succeeds in leading the others to the room, and it doesn't work like he promised, he has little left to argue his point.
You could even relate this to the experience of viewing the film itself (or films of this nature). I personally love this film, even (at the risk of sounding pretentious) for some reasons I don't fully understand. Yet I have a hard time recommending it to some people I know given its deliberate pace and experimental nature. Getting someone to watch the film is a bit like taking them to the room, and after they have seen it, it is difficult to argue what it is or isn't (in particular, if they aren't interested in hearing it) though their perception of it will depend a lot on where they happen to be (spiritually, if you will) at the time they experience it. Of course, the film (or the room) doesn't change, but the individual can change with time and become more in tune with what is happening in the "room" and then finally see what Stalker was after the whole time.
Which brings us to the end.
Stalker's efforts may seem to have failed at face value, but I think the end scene with Monkey shows the real power of the Zone, and the fact that there is still hope for the others to come around to it. Again, in lesser hands, this could have been a simple case of Stalker not being able to convince the Scientist and the Writer, but oh, look what Monkey can do--I guess Stalker was right all along. And maybe there is still some element of this in the film (if not that Stalker was "right all along" then at least that there is something going on that no one can completely explain with just their backgrounds as Scientists, Writers, or, um, Stalkers). But for me, even if this last image is meant to convey this sentiment (a la the "...but it did happen" at the end of PTA's Magnolia), I'm willing to forgive it just for how, for lack of a better word, "cool" it looks.
Anyway, that is just one of many interpretations (hopefully not too simplistic) that I think can be reasonably supported. I might pull out something totally different if I sat down and tried writing out my thoughts on the film again. (Just like the film might have been totally different if the first print hadn't been ruined!) But I've already said enough for now...
