Maybe this will work.
void displayRollPitchYaw(RTVector3& vec)
{
Serial.print(vec.x() * RTMATH_RAD_TO_DEGREE);
Serial.print(' ');
Serial.print(vec.y() * RTMATH_RAD_TO_DEGREE);
Serial.print(' ');
Serial.println(vec.z() * RTMATH_RAD_TO_DEGREE);
}
...
displayRollPitchYaw((RTVector3&)fusion.getFusionPose());