First time login redirect - amend code only for 'subscriber' user role

Question

I'm using the code below to redirect users to a welcome page upon their first login. It works a treat, but I need to apply it to the 'subscriber' user role only.

add_action( 'user_register', 'myplugin_registration_save', 10, 1 );

function myplugin_registration_save( $user_id ) {

    // insert meta that user not logged in first time
    update_user_meta($user_id, 'prefix_first_login', '1');

}

// hook when user logs in
add_action('wp_login', 'your_function', 10, 2);

function your_function($user_login, $user) {

    $user_id = $user->ID ;
    // getting prev. saved meta
    $first_login = get_user_meta($user_id, 'prefix_first_login', true);
    // if first time login
    if( $first_login == '1' )  {
        // update meta after first login
        update_user_meta($user_id, 'prefix_first_login', '0');
        // redirect to given URL
        wp_redirect( 'http://www.example-url.com' );
        exit;
    }
} 

Bearing in mind I don't know anything, to me it seems like I need to add another 'if' element. I.e. If 'it's the user's first-time login' and 'the user has a subscriber role'. But I've no idea!

Please could someone help me amend this?