2000 Alfa Romeo 156 car wont start

Engine Mechanical problem
2000 Alfa Romeo 156 4 cyl Front Wheel Drive Manual

my alfa romeo was driving on motorway at 60mph when the engine stopped and stalled and rolled to the side of the motorway. When trying to start their is a bang from the bottom of the engine and the car wont attempt to start. There is oil in the engine, all fluid levels are good and it selects all tghe gears and clutch works perfectly. A friend told me to put the car into 3rd gear and try and roll in back and forth to make sure it isnt seized and the car moved so dont think its seized. Any possible answers please? Thanks Barry Carter