Jump over to Settings and then the Rooms tab. At the bottom of the page is a button called Reorder room.
From here, you can drag and drop on the rooms around the page to change the order on the grid. We find that most people prefer:
Numerical ordering or
Room type ordering
Once you're done, just click Save changes and head back to the grid. You may need to refresh your page to see the changes (hold the control/command key and the 'R' key together).
Reorder Room Types
You can reorder Room Types by going to Settings > Rooms and clicking 'Reorder room type'.