How to roll a ball ?

A simple way would be to use transform.Translate as well as transform.Rotate, so that the ball rotated as it moved:

 // Moves ball along the X and rotates on the z to simulate rolling
 transform.Translate(5, 0, 0);
 transform.Rotate(0, 0, 5);

Obviously that's REALLY basic and you'd need to tweak the math but shouldn't be too hard to get going.

The right way to roll the ball it is roll ball to the way with your camera will faced...So for this I wrote the code on c# witch will move the ball always in right way,the way witch look your camera..Sooo

public float ballSpeed = 10.0f;

void FixedUpdate(){

 if(input.GetKeyDown(KeyCode.W)){
    this.rigidbody.AddForce(Camera.main.transform.forward * ballSpeed);
 }

  if(input.GetKeyDown(KeyCode.S)){
    this.rigidbody.AddForce(-Camera.main.transform.forward * ballSpeed);
 }

  if(input.GetKeyDown(KeyCode.A)){
    this.rigidbody.AddForce(-Camera.main.transform.right * ballSpeed);
 }

  if(input.GetKeyDown(KeyCode.D)){
    this.rigidbody.AddForce(Camera.main.transform.right * ballSpeed);
 }

}

add to the sphere a rigid body and use this code:

 public float speed;
     void FixedUpdate (){
 
     float moveHorizontal = Input.GetAxis("Horizontal");
 
     float moveVertical = Input.GetAxis("Vertical");
 
     Vector3 movement = new Vector3(moveHorizontal, 0.0f, moveVertical);
 
     rigidbody.AddForce(movement * speed * Time.deltaTime);
     }