How to move the object to where the object is already pointing to?

Hey guys,
I created a script for my player, so he can rotate on the z axis on “Rotation” (a, d) and player can move left to right on Horizontal (Left Arrow, Right Arrow). I also set it so the player is automatically moving up.
I am wondering if I rotated left or right on z axis, how am I able to move the player to that direction because right now when I rotate left or right, the player still moves straight up.

Here is my Code

    // Player Speed
    float speed = 450;
    float forwardSpeed = 40;
    float rotateSpeed = 100;
    // Player Rigidbody
    Rigidbody2D rb;
    // Launch Button, Launch Button Gameobject and set launch to false
    public GameObject launchButton;
    Button lb;
    bool launch = false;

    void Start () {
        // Get Rigidbody and button component from gameObject
        rb = GetComponent<Rigidbody2D>();
        lb = launchButton.GetComponent<Button>();
	void FixedUpdate () {
        // Set player movement controls
        float Horizontal = Input.GetAxis("Horizontal");
        float Rotation = Input.GetAxis("Rotation");
        //Launch Button (on click go to LaunchButton method)

        if (launch == true) // if launch equals true then 
            //move player upwards, left or right;
            rb.velocity = new Vector3(Horizontal * speed, forwardSpeed, 0) * Time.deltaTime;

            //rotate player left or right
            transform.Rotate(0, 0, Input.GetAxis("Rotation") * rotateSpeed * Time.deltaTime);


Thanks guys for your help

Transform.Translate using Space.Self, or if you use Physics, RigidBody.AddRelativeForce.