Roll/Dodge/Evade System

I am trying to make my character be able to evade attacks. My movement script is quite long but this is the portion of code I am using.

 if(evading)
         {
             moveDirection = playerRotation.transform.forward / 5 * evadeSpeed;
             moveSpeed = evadeSpeed;
         }

The problem here is that I don't have control over the two things I need:

The distance of the roll and the speed in which the character covers the distance. I am uncertain how to control these.

@HappyMoo's comment : The evasion occurs in the forward direction because the forward direction is the direction the character is facing, that's the style I want for my game.

     void ProcessEvasionTime()
     {
         //evasion timer for action performed
         if(evading)
         {
             evadeTimer -= Time.deltaTime;
             if(evadeTimer <= 0)
             {
                 anim.SetBool("Evading", false);
                 evading = false;
                 cooldownInEffect = true;

             }
         }else
         {
             evadeTimer = evadeTime;
         }

         if(!evading && InputManager.ActiveDevice.GetControl(InputControlType.Action1))
         {
             ProcessEvasion();
         }

         if(cooldownInEffect)
         {
             cooldownTimer -= Time.deltaTime;
             if(cooldownTimer <= 0)
             {
                 cooldownInEffect = false;
                 cooldownTimer = cooldown;
             }
         }
     }

     void ProcessEvasion()
     {
         if(!cooldownInEffect)
         {
             //timers
             evading = true;
             evadeTimer = evadeTime;

             //move character to evade and set animator to play evasion animation
             anim.SetBool("Evading", true);
         }
     }

Character Movement: Note - The input system is a custom script to allow cross controller support, just think of it as input.getaxis or relevant alternative.

     void Update()
     {
         InputManager.Update();

         //cache the inputs
         //h = Input.GetAxis ("Horizontal");
         h = InputManager.ActiveDevice.GetControl(InputControlType.LeftStickX);
         //v = Input.GetAxis ("Vertical");
         v = InputManager.ActiveDevice.GetControl(InputControlType.LeftStickY);
         //s = Input.GetAxis ("Strafe");
         //mh = Input.GetAxis ("Mouse X");

         //zero the move direction so previous data is removed
         moveDirection = Vector3.zero;

         //check if it's grounded, otherwise player cannot move, also check for the deadzone
         if(characterController.isGrounded)
         {
             if (v > deadZone || v < -deadZone)
             {
                 moveDirection = new Vector3 (0f, 0f, v);
             }
             //add horizontal movement to the (currently)vertical movement vector
             moveDirection.x = h;
             //process turning
             //ProcessTurning(s, mh);

             //normalize the diagonal inputs to prevent values above 1
             if (moveDirection.magnitude > 1)
             {
                 moveDirection.Normalize ();
             }

             //move character in the direction of the camera's facing angle
             moveDirection = cam.transform.TransformDirection(moveDirection);
         }

         //change movement speed if weapon unsheathed
         if(anim.GetBool("Unsheathed") == true && !evading)
             moveSpeed = walkSpeed;
         else
             moveSpeed = runSpeed;

         //process evasion timers
         if(combo!= null && combo.attackTimer <= 0)
             ProcessEvasionTime();

         //all events for when the player loses control of character eg. talking, cutscene, death, evading
         RevokeControl();

         //set the animator's Speed float to the magnitude of the moveDirection to allow for the run animation to play
         anim.SetFloat ("Speed", moveDirection.magnitude);

         //calculate gravity
         moveDirection.y = -gravity * Time.deltaTime;

         //move the character
         characterController.Move (moveDirection * moveSpeed * Time.deltaTime);
         transform.Rotate(turnDirection * Time.deltaTime);

         //control player facing direction when strafing, moving backward, etc
         if(moveDirection.x > deadZone || moveDirection.x < -deadZone || moveDirection.z > deadZone || moveDirection.z < -deadZone)
         {
             desiredRotation = Quaternion.LookRotation(new Vector3(moveDirection.x, 0f, moveDirection.z));
             playerRotation.transform.rotation = Quaternion.RotateTowards(playerRotation.transform.rotation, desiredRotation, rotateSpeed * 10 * Time.deltaTime);
         }
     }