Well I think Robo answered one part of this really well... the fact that we already have loads of rooms that aren't always that busy, it might be a good idea to wait a bit. Sometimes we go to the effort of adding rooms as per chatters request, and then it never gets used.
I think this simply boils down to learning to be patient with others and sharing. If you are having such an intense conversation, that you just simply cant deal with the other people who enter wanting idle chit-chat, then those who involved in the intense convo, could just move it to another room. Usually people don't just come into a room and start 'talking about their dog' .. most people come in and ask 'Hey, what's the topic?' or they sit and listen awhile to see if they're interested in the topic, or if they wanna switch rooms.
So, just carry on with your conversation. If someone truly is being disruptive, then let a mod know, but if they just don't want to talk about what you're talking about, that's not such an issue. We need to remember there are thousands of users on this site, so we all have to try and be considerate of each other.
I would also like to point out that implementing a new room isn't as easy as you may think it is, and we don't have the mods to 'police' this room as you suggested. As Mods, we don't have the time to put all of our focus in one spot for hours on end, while other needs get neglected. There are many other things we need to attend to, alot of them are unseen 'behind the scenes' things, that help keep this site up and running.
I hope that helps