Generally, on a road ride, I just carry enough stuff with me to fix one flat tire. No multi tool.

On the other hand, I've been wrenching bikes for a lot of years and I'm pretty attentive to unusual noises and such. On every ride I make a mental note of any maintenance that needs doing on that particular bike and I'm pretty good about seeing to it before I ride that bike again. In other words, I prefer to do my bike fixing at home.

In the interest of full disclosure I do carry a Park mini-tool kit, and even a few carefully selected spares, on my tandem and on my mountain bike.