As a GM, you want to be able to control what information goes out to your players and what is kept private to you alone.  There are several tools in d20pro that help you control what information players receive.

Story & Boxed Text

You can use the Boxed Text tool to type or paste text for the players. It will appear in a different font in the Game Log.

Global Dice Rolls

If you want to turn off the display of all d20 rolls to the players, click on the icon in the top left corner of your map window.  The icon will change to reveal the current setting and you will receive a notification of the current state as well.  Hidden rolls have a hand over the die, while visible rolls show an eye.  This function is useful if you want to have an NPC make a bluff check, or a player wants to make a listen check (and you don't want them to metagame).  Remember to turn rolls back on if you want players to be able to see their rolls!

If you just want to hide NPC rolls from the PCs, click the Options button (golden gear icon) and the Judge Options section in the panel.  Then uncheck Show NPC Rolls.

GM Tip: One thing to remember is that players don't see the die rolls of hidden creatures that they do not control.  So if you want to make a secret bluff check for an NPC and you don't want the Players to even know that you made a roll, hide the creature before you roll, then quickly reveal it. Unless the players or you move, the visibility state of the NPC will never be sent to the players. So they won't see the NPC disappear while you make the skill roll.