Random movement attempt

I'm trying to make my bear walk randomly when the player is not in it's range. I wanted it to randomly select the its rotation in y axis and then move it forward and after some time switch the rotation randomly again.

The thing is that I don't really know how could I assing him a random rotation. Could anyone help me with it please? Every bit of help would be much appreciated.

var distance : float;
var playerm : GameObject;
private var playerGUI : PlayerGUI;
var target : Transform;

var aggroRange : float = 30;
var moveSpeed : float = 4.0;
var health : int = 120;
var attackRange : float = 3.0;
var damage : float = 0.1;
var cooldown : float = 10.0;
var roll : int;
var delay : float = 2;

private var timeToChangeDirection : float;
private var angle : float;

var damping : float = 6.0;
var gravity : float = 100.0;
private var moveDirection : Vector3 = Vector3.zero;

var controller : CharacterController;

function Start()
{
    playerm = GameObject.Find("Player_Model");
    target = playerm.transform;
    playerGUI = GameObject.Find("First Person Controller").GetComponent(PlayerGUI);
}

function Update()
{
    if(health <= 0)
    {
        delay -= 0.1;
        animation.Play("Dead");
        if(delay <= 0)
        {
        Destroy(this.gameObject);
        }
    }

    distance = Vector3.Distance(target.position, transform.position);

    if(distance > aggroRange)
    {
        //Stop();
        timeToChangeDirection -= Time.deltaTime;

         if (timeToChangeDirection <= 0) 
         {
         ChangeDirection();
       }

       controller.Move(transform.forward * Time.deltaTime);
    }

    if(distance < aggroRange && (distance > attackRange) && (cooldown <= 0))
    {
        LookAt();
        Chase();
    }

    if(distance <= attackRange)
    {
        if(cooldown <= 0)
        {
            Attack();
        }
    }

    if(cooldown >= 0)
    {
        cooldown -= 0.1;
    }
}

function LookAt()
{
    var rotation = Quaternion.LookRotation(target.position - transform.position);
    transform.rotation = Quaternion.Slerp(transform.rotation, rotation, Time.deltaTime * damping);
}

function Chase()
{
    animation.Play("Run");
    moveDirection = transform.forward;
    moveDirection *= moveSpeed;

    moveDirection.y -= gravity * Time.deltaTime;
    controller.Move(moveDirection * Time.deltaTime);
}

function Stop()
{
    animation.Play("Idle");
    animation["Idle"].speed = 0.5;
}

function Attack()
{
    roll = Random.Range(0, 2);
    if(roll == 1)
    {
        animation.Play("Maul");
        playerGUI.healthBarDisplay -= 0.2;
    }
    else
    {
        animation.Play("Bite");
        playerGUI.healthBarDisplay -= 0.1;
    }
    cooldown = 10.0;
}

function Movement()
{

}

function ChangeDirection()
{
    //angle = Quaternion.Slerp(transform.position);
    //transform.rotation = Quaternion.Slerp(transform.rotation, angle, Time.deltaTime * damping);
}

Thanks in advance.