I am wanting to create a new ArcMap Add-In project with just a custom root menu. According to the walkthrough, I can access the Add-In Command Bars (which has the Menu element) by adding a new item to a project. What kind of project do I create in the first place given the selection of Add-In Types?
I don't think you can create an actual menu item in the main menu bar with add-ins. You can create a toolbar though and put all your custom add-ins (menu, buttons, combo box) on the toolbar.
See "Creating a custom toolbar"