The "dice tray", that is, the dice near the bottom of the EpicTable window, allow you to roll dice quickly.  What can you do with it?

1. Click a die and hit a number to roll that many of that die to the chat window.  
2. Drag a die to a tabletop.  They copy-on-drag, so you won't lose them.  Dice on the tabletop are good for games like Dogs in the Vineyard.