I recently ran across this short (13:15) video tutorial describing the process and math of figuring out your position and orientation from an IMU. It was a quick overview at just the right level of detail to connect a lot of the different concepts that I have been thinking about for the rover project.
For the rover, simply getting orientation information out of an AHRS algorithm isn't going to be enough. I also need acceleration values (in the inertial frame) with gravity subtracted out, to be able to plug into the Kalman filter. In essence, since the rover doesn't have wheel encoders, I'm using the IMU's acceleration to help do dead reckoning.
If you put that video together with an AHRS algorithm like Madgwick or Mahoney, and then take a look at the coordinate transformation sections in the rather famous book "The Global Positioning System & Inertial Navigation," you'll get a pretty good overview of how my robot will know where it is and where it's pointing.