Hi FSXFan, welcome aboard!
I am not a pilot but will hazard a guess at the roaring noise. IF, and only IF the aircraft WAS an MD-80, then remember that the engines are right at the back and set one either side, just outside where the toilets are.
When transiting a variable wind system, it may be necessary for the flight crew (or automatic systems) to vary the power setting of the engines in order to maintain a stable flight level. If a small climb in height was needed, then the engine power would also increase and certainly give a roaring sound. Consider how the 'roaring' was during take off and this period of flight.
As I say, this is a guess and best wait for flight crew to confirm or tell me to get back where I belong!