Several ways.

One could be triggers, put a dummy object in the entrance / door of the room and assign an action / function to trigger the event when the player touches the objec.

Ex:

Code:

---

function my_event
{
   if ( EVENT_TYPE == EVENT_ENTITY )&&( you == room1)
   {
       my._roomPos = 1;
       // other functions
   }
}

---

In player action put:

my.enable_entity = on;
my.event = my_event;

In rooms dummy action:

my.passable = on;
my.enable_entity = on;