If you are not seeing the Nav Menu Roles options on your menu items, it is likely that you have another plugin that is also trying to alter the same code that creates the Menu section in the admin (for example the UberMenu mega menus plugin).
This is not a failure of Nav Menu Roles and there isn't anything I can do about it. WordPress does not have sufficient hooks in this area of the admin and until they do plugins are forced to replace everything via custom admin menu Walker, of which there can be only one. Until these hooks are added the menu modification plugins are unfortunately going to conflict with one another.
There's a possibility this will be added in WordPress 3.6
When/if it is, I will update Nav Menu Roles.