Looks like you're using Multisite, I would encourage you to visit Central Geek if not done already, and get in touch with my friend Louis there, he's the "multisite" expert of our team. Especially when your questions in these posts essentially belong to the "how to" category rather than to the "doesn't work" one...
About your other considerations. If you activate the Network Toolbar from the "Network" tab, it will show forcibly network wide without site admins being able to hide it. Alternatively, if you visit the "Sites" tab, you may hide the "Toolbar" options tab from sites where you want to force the display of the Toolbar, and then from your Main Site, "Toolbar" tab, check "Force the display of the Toolbar". This setting will be mirrored to all the subsites where this options tab is hidden. Note that hiding the "Toolbar" tab from subsites will equally mirror that setting and all the other settings available at this tab, from the Main Site to those subsites.
It is important to stress that this corresponds to two different use cases. The first one means "I'm the boss in my network", the other gives a little flexibility to site admins, which in return assumes they can use it, e.g. to hide the Toolbar or any of its default items. If using network menus, or willing to show anything network wide, I would strongly suggest to use the Network Toolbar feature to ensure the Toolbar will be displayed network wide. You may have to make a balance between all your needs :)
About your last question. If you want to add items to a menu depending on roles, you should consider adding different menus to the same location, and set their roles accordingly. This should also work for network menus, and overimposing site menus above network menus. There are also hooks that you may use, esp. one to make a menu item, a location for subsites' custom menus, which can be useful for multisite installs - look for "symposium_toolbar_init_globals_done" in the Dev Guide.
Last but not least, the issue of responsiveness has been brought to my attention through another topic: under 783px width, all Toolbar items but the WP Logo and User Menu ("My Account") will be hidden by WordPress. This is important enough for me to put this on top of my TODO list, but not to delay any further the v27 that is now ready for upload with plenty of new features and bug fixes, thanks to user inputs :)