Maybe it is because I do build my own - though I won't put myself in the same category of most of you guys - in terms of quality or quantity. It is strictly a hobby.
To the point of having a manager, agent, whatever you may call them, the only downside I see is that, for me anyway, I would want to talk to the person who is going to being the buid, look at and feel the wood and pretend that I know something about the work involved. I have no idea if there are enough people out there who feel the same way to the point that it would make a difference in the big picture or not. The deal with your roommate sounds like a no brainer, exposure at shows can open the doors and get your name and your work out there.
Here is a hint, in my working life, I worked for the Yellow Pages and got stuck working a trade show for plumbing contractors - some seriously big money people were there. We had some kind of $.99 giveaway, I don't even remember what it was and we had people lined up to get one. Thr something like a ping pong ball drawing - if they get the "magic ball" they win a set of strings, if not they win a couple of picks. These guys just thought it was great. And spend a few bucks and get your name and logo printed on the picks. Name recognition.