You draw just one card, no matter how many creature cards the player mills beyond the first.

The player dealt combat damage mills cards only for the damage dealt by your Rogues, not for any other combat damage dealt to them at the same time.

Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to other Rogues you control may become lethal if Anowon leaves the battlefield during that turn.

If Rogues you control deal combat damage to two players at once, Anowon’s ability triggers twice.