Currently, it is not possible to configure which icon a rollup displays. This presents a usability issue when a caller wants to defer loading of a rollup's contents. In such a scenario, the caller may want to add a single component (the heading) up front, but add the content component at a later time. Until the content is actually loaded, the rollup displays a bullet icon rather than an expander icon. Current workaround is to load a dummy content component up front and replace it with the actual content when the rollup is first expanded.