Those measurements ate a rise over run calculation. For every 12" of horizontal progression, the roof moves up 9" (for 9/12).

If you want to know the angle of your roof, you can do several things. You can measure it from within by accessing the roof rafters from your attic (they'll have the same rise/run as the exterior), you can try to work with a photograph and manipulate it in photoshop to find the angle. You could measure the peak of your roof and the soffit to find the angle.

There are more eccentric approaches; you could toss a ball up there and time how long it takes to roll back down, and use that time to determine acceleration, normal forces, and isolate the angle. You could also measure the shadow cast by your roof.

If you measure an angle, 12*tan(theta) will give you the rise.