How to make a reloading time because now i can shoot unlimited

You need a cool down of some sort.

  using UnityEngine;
  using System.Collections;
  
  public class RocketSpawnSource : MonoBehaviour {
      public GameObject RocketPrefab;
      public static bool rocketShooted;
      public int RocketCoolDown = 5; // Used to assign in editor and reset the rocketCoolDownCount.
          
      private int rocketCoolDownCount;
          
      // Use this for initialization
      void Start () {
                 rocketCoolDownCount = RocketCoolDown; // initialize the Cool down count.
      }
      
      // Update is called once per frame
      void Update () {
  
          if (Input.GetMouseButtonDown(0))
          {
              if (rocketCoolDownCount > 0)
              {
                  rocketCoolDownCount--;
              }
              else
              {
                  Instantiate(RocketPrefab,transform.position,transform.rotation);
                  StartCoroutine("RocketShooted");
              }
          }
      }
  }

 

In your RocketShooted method that you didn't include here, you need to reset the rocketCoolDownCount to RocketCoolDown.

 // in your RocketShooted method, after shooting
 rocketCoolDownCount = RocketCoolDown;

 float shootDelay = 0.2f;
 float currentDelay; 
 
 void Start()
 {
 currentDelay = Time.time + shootDelay;
 }
 
 void Update () {
  
          if (Input.GetMouseButtonDown(0))
  
          {
            if(Time.time > currentDelay)
              {
              Instantiate(RocketPrefab,transform.position,transform.rotation);
              StartCoroutine("RocketShooted");
              currentDelay = Time.time + shootDelay;
              }
  
          }
      }