Multiple questions about Betrayal at the House on the Hill
When the haunt begins, the player to the left of the traitor always takes the first turn. It doesn't matter who had the last turn (the person to reveal the haunt will not always be the traitor). There are a couple scenarios that change this, but they will specify their own rules in the haunt description. Rulebook, page 11:


  Haunt Turn Order
  The first turn always starts with the player to the traitor’s
  left and goes clockwise (further away from the traitor).

The monsters get their own "monster turn" after the traitor's turn. So the traitor does not control both himself and the monsters in the same turn, but he does control all the monsters right after he's done with his regular turn. Rulebook, page 11:


  After each hero has had a turn, the traitor gets his or hertraitor turn. After the traitor’s turn, any monsters controlled by the traitor get a monster turn. (One player gets two turns: one for the traitor and one for the monsters.

All information always openly shared between the heroes. So it doesn't matter which hero found the clue and has the knowledge roll token; all that matters is the total number of knowledge roll tokens found by all heroes combined. From the FAQ:


  If someone in the house makes a knowledge roll to find out a particular piece of information (a mummy's name, a room that needs to be visited, etc.), do all the other explorers know this information automatically?
  
  
    Yes. Perhaps they all have walkie-talkies.