Sakashima's Student and Stinkdrinker Bandit
No, the Ninjutsu'd Stinkdrinker Bandit's ability will not trigger.

Stinkdrinker Bandit's ability is a triggered ability. When the defending player has decided on his blockers, it triggers for every Rogue that is now unblocked. It will not trigger again during the current combat phase.

If you want to Ninjutsu your Stinkdrinker Bandit with Sakashima's Student, you can only do so after blockers have already been declared because of Ninjutsu's  timing restrictions: An unblocked creature is any attacking creature that, after the blockers have been declared, has not been assigned a blocker. By that time, it's too late for the copied Stinkdrinker Bandit to trigger his ability.

For your combo to work, Stinkdrinker Bandit's ability would have to be a static ability and read something like "Attacking and unblocked Rogues you control get +2/+1". In that case, it wouldn't matter when the Stinkdrinker Bandit would enter the battlefield, as long as it's before the end of combat.