There is a option to customizing root node with EDITORIAL, GRID, or LIST using presentation map like below
<?xml version="1.0" encoding="UTF-8"?>
<Presentation>
. . .
<PresentationMap type="DisplayType">
<RootNodeDisplayType>
<DisplayMode>GRID</DisplayMode>
</RootNodeDisplayType>
. . .
</PresentationMap>
. . .
</Presentation>