How to rotate the game object

I have done the drag the game object in the camera applying mesh collider but how to rotate my gameobject.

 using UnityEngine;
 using System.Collections;
 
 public class MyDragBehaviour : MonoBehaviour 
 {
     private float maxPickingDistance = 2000;// increase if needed, depending on your scene size
     
     private Transform pickedObject = null;
     
     // Use this for initialization
     void Start () 
     {
     }
     
     // Update is called once per frame
     void Update () 
     {
         foreach (Touch touch in Input.touches) 
         {
             Debug.Log("Touching at: " + touch.position);
             
             //Gets the ray at position where the screen is touched
             Ray ray = Camera.main.ScreenPointToRay(touch.position);
             
             if (touch.phase == TouchPhase.Began) 
             {
                 Debug.Log("Touch phase began at: " + touch.position);
                 
                 RaycastHit hit = new RaycastHit();
                 if (Physics.Raycast(ray, out hit, maxPickingDistance)) 
                 { 
                     pickedObject = hit.transform;                    
                 } 
                 else
                 {
                     pickedObject = null;
                 }
             } 
             else if (touch.phase == TouchPhase.Moved) 
             {
                 Debug.Log("Touch phase Moved");
                 
                 if (pickedObject != null) 
                 {
                     Vector2 screenDelta = touch.deltaPosition;
                     
                     float halfScreenWidth = 0.5f * Screen.width;
                     float halfScreenHeight = 0.5f * Screen.height;
                     
                     float dx = screenDelta.x / halfScreenWidth;
                     float dy = screenDelta.y / halfScreenHeight;
                     
                     Vector3 objectToCamera = 
                         pickedObject.transform.position - Camera.main.transform.position;
                     float distance = objectToCamera.magnitude;
                     
                     float fovRad = Camera.main.fieldOfView * Mathf.Deg2Rad;
                     float motionScale = distance * Mathf.Tan(fovRad/2);
                     
                     Vector3 translationInCameraRef = 
                         new Vector3(motionScale * dx, motionScale * dy, 0);
                     
                     Vector3 translationInWorldRef =
                         Camera.main.transform.TransformDirection(translationInCameraRef);
                     
                     pickedObject.position += translationInWorldRef;
                 }
             } 
             else if (touch.phase == TouchPhase.Ended) 
             {
                 Debug.Log("Touch phase Ended");
                 
                 pickedObject = null;
             }
         }
     }
 }