I actually find rotaries more negotiable, in general, on a bicycle than in a car. In a car they're awful at times because so many people are confused by them that they often slow or stop unnecessarily or abruptly.

I'm a chain tool carrier but the last time I went to use mine I realized it was so old and the drive pin was loose and bent. So, if you carry one don't be like me carry one that's in good shape. And I find any chain problem to be a real bear when my hands are cold or it's freezing out.

edit: oh the pliers thing... if I need them I carry a Leatherman juice CS4- good for sawing unruly branches on the bike path and opening bottles of wine as well.