Well its also not quite that, as the force of the heli is not tangent to the circle, its straight in, pretty much perpendicular to the circle. If you stop rolling it doesn't make a slide motion, it flies 'up' relative to the skids.
You could probably draw how the heli makes a circle by drawing straight lines on a piece of paper, first imagine making a square with the heli nose up. You apply collective making a vertical line on the paper down on the left side. Roll the heli 90 degrees and again grab some collective. Now you draw a horizontal line left to right on the bottom edge of the paper. Another 90 roll, vertical line up the right side of the paper. Another 90, horizontal line right to left up at the top of the paper. Thats the rough forces its using. Split the 90s to 45s and its an octagon, closer to a circle, split those 45s and i don't know what you call it anymore =D. Split those, and again, and again, eventually its a circle. The heli is always trying to go past the center a bit, but never can since you keep rolling it, there should be a smaller circle inside the circle the heli makes where the rotors are aiming for.
