Cargo
Can we stop all these nonsense theories about cargo theft?
If anyone had enough advance knowledge of the cargo and the flight it was carried on to plan to hijack the plane, they would have saved themselves a hell of a lot of money, risk and trouble by hijacking the truck that took it to or from the airport.
The only part the cargo has to play in the solving of this mystery is if it was in some way responsible for causing an explosion, fire or other incident in flight.
Oh and on the subject of the 'roger that' reply, do we know that the pilot making that comment was speaking English? If he was talking to Malaysian ATC he may have been speaking Malay and the above may simply be a poor translation into English.