Rotate a GameObject in the Vector3 direction?

I am making a mobile game and everything is working but the character rotation.
I got the movement code which uses the Unity Standard Assets joystick to move the character around.

		vertical = CrossPlatformInputManager.GetAxisRaw ("Vertical");
		horizontal = CrossPlatformInputManager.GetAxisRaw ("Horizontal");

		Vector3 playermovement  = new Vector3 (horizontal,player.position.y*0f, vertical);
		playerbody.AddForce (playermovement*speed);

This works great and the player is moving in the exact position I go with the mobile joystick but I want the player to also rotate in the direction it’s going on the Y axis. For example to rotate right and left etc…
I tried messing around with quaternions but I cannot get it to work…

void Update () {
transform.rotation = Quaternion.LookRotation (Vector3.RotateTowards (transform.forward, playermovement, 5 *Time.deltaTime, 0.0F));
}