You need to load the VG_AHRS Application which runs Kalman Filter and estimates the Roll and Pitch.
The OpenIMU300RI ships by default with IMU only.
The compiled code is on this page and can be directly installed from the website if the devices is connected via the Python driver.
The FW code is also in Visual Studio Code Aceinna Extensions and can be compiled and loaded from source
Home -> Custom IMU Examples -> OpenIMU300RI/VG_AHRS