You can tell Rover to display 1, 2, 3, 4, or 5 listings across by setting that preference globally in Rover IDX >> Styling >> Listing Layout. 

If you want to override that global setting for a specific page, just add listings_per_row="2" to your shortcode.

The value of listings_per_row is a percentage of the 100% row width.  So if you want to display 2 listings in a row, you should type listings_per_row="50" - each listing being 50% of the width of the row.

 

How many listings across the row Setting
1 listings_per_row="100"
2 listings_per_row="50"
3 listings_per_row="33"
4 listings_per_row="25"
5 listings_per_row="20"

 
* The old parameter `cube_width` still works, but not not preferred.