It means everyone else passed on it and the person who rolled Greed got it because no one else needed it.
Edit: You might want to check your Chat/Log settings on the Character Customization settings. You may not have those messages to show up. I'd suggest right clicking the "General" chat on the settings and setting it to default General Settings. Click the cog on the Chat window which should open the settings I am talking about.
Ahh, it all makes total sense now. Thanks everybody for explaining this to me. I'll sure keep an eye on the chat window during my next dungeon.
As for the main game, I just arrived at the Scions of the Seventh Dawn, and I find them so cool. And the plot is interesting although still very bare-bones.