[GhotiFish]

There are two competing methods of navigation in blender that have to do with this point.

Turntable and Trackball.

fairly intuitive names for the concept, turntable keeps one axis fixed, and lets you rotate on the other two, and trackball behaves, well, like a track ball. Much like this demo.

The turntable is much simpler, but the trackball is much more capable (if a little tricky to use).

If you use it for a bit of time however, you'll find that despite only have two degrees of freedom, you're capable somewhat indirectly controlling the roll of your camera by click and dragging in a circle.

Test it on the globe! Grab a point and move your mouse in a circle, the larger the circle the faster the roll. It's actually pretty intuitive when you get used to it.

Which is why the debate between Turntable and Trackball exists. They both have merit.