Newsletter, since version 6.1.2, can be used by different WordPress roles and no more only by editors and administrators. We extended the roles selection specially for ecommerce sites, implemented with WooCommerce, which have a number of extra roles, like the Shop Manager.
Those roles could be reasonably allowed to manage the site newsletters.
That said, on main Newsletter settings there is now a list of roles, standard and defined by third party plugins, which can be selected and allowed to manage part of the Newsletter administration features.
Of course the Administrator role is always allowed to access to everything, while other roles, when enabled are limited to the “editing” features. So they cannot access the main settings or the integration with external delivery systems.
Let us know if this new feature meet your requirements about access control to Newsletter administration panels or if you have even more specific needs.