Custom Capability – show plugin menu to these users and admins only

Hi,
I have created a plugin which has custom menu pages.
The plugin creates two roles upon activation (let’s say role 1 and role 2).

role 1 is used for some coding and works fine, WordPress users are assigned this role and the code works correctly.

Where I am struggling is that I would the plugin menu’s to only be displayed to Administrators and users who have role 2 assigned to them.

I am running the following from a function called by my activation hook…

add_role( 'role 1', 'Role 1', array( 'read' => true, 'level_0' => true ) );
		add_role( 'role 2', 'role 2', array( 'read' => true, 'level_0' => true ) );
		add_action( 'admin_init', 'f_mdjm_caps');

the function f_mdjm_caps contains the following

function f_mdjm_caps()	{ /* Capabilities */
		$role = get_role( 'role 2' );
		$role->add_cap( 'manage_myplugin' );
	}

I tried adjusting my menu code to be

add_menu_page( 'My Menu', 'My Menu', 'manage_myplugin', 'mdjm-dashboard', 'f_mdjm_admin_dashboard' );

but the menu disappears.

Any help appreciated

Thanks!