Open rolling as far as I know.  The only exception would be for the pieces of the epic mace.  The healers will roll for the first one and then that person gets all the pieces until it's completed.  Then the next person to win the roll on the first piece does the same and so on.  

Usually this type of rolling works itself out.  It sucks to lose out on gear to someone that is getting a very slight upgrade while it would have been HUGE for you, but I've found that MOST of the time, people in a guild care about the progression as much as themselves and are usually cool about rolling.

The exception to this rule, and I hope everyone agrees, is a best in slot item.  I don't think hunters should be rolling on a fist weapon that is a best in slot for a shaman and warriors and rogues should not be rolling on bows and guns that a hunter needs.  

The other exception would be for well geared alts.  Everyone needs to decide up front who their main is.  Any toon considered an &quot;alt&quot; should be passing on gear for someone else's main.  Not that this is going to be an issue for a while, but I think something should be established up front.  One thing I don't like seeing is somebody gearing up two toons while one of our mains just festers because of poor rolling.  It comes back to the second reason no one likes to bring pugs, they roll on loot, win it and then never show up again and then our mains are rolling against new people again.  Very frustrating and I think we should protect our mains at least in this.