There are a vast variety of rooms in The Binding of Isaac, and each expansion to the game only adds more. Dice Rooms have been around forever and they are a neat way of randomizing your run. As with most things involving dice, it's a gamble.
There are six different Dice Room configurations in the game, each corresponding with a face of a d6 and its own effect. It can be annoying to remember what each room does, but there are some handy signs that can act as reminders if you have the Afterbirth+ expansion.
Dice Rooms cost two keys to enter. If you have the Repentance expansion installed, they will have red doors with a die above them. You can safely enter a Dice Room without any of its effects triggering - to use a Dice Room you need to walk over the large die icon in the middle of the floor. The screen will shake and the room's effect will resolve. All Dice Rooms can only be used once.
Dice Room One
This room mimics the D4 item. Stepping onto the die will reroll all of Isaac's collected items into random ones. These items will be from the item's original room pool - for example, you could reroll The Book of Belial into Brimstone.
Activated items can be rerolled into passive items, but the reverse is not true.
There will be a small marker resembling the D4 item in this room to remind you of the room's effect.
Dice Room Two
Like the one-pip room, this Dice Room mimics the effect of a dice item. Stepping onto the die in this room will trigger the D20 effect - this will reroll every pickup (i.e. Hearts, Coins, Keys, Bombs, etc.) in the room. These rooms will spawn with pickups in for you to reroll, but it's possible to ignore the die completely and just pick the pickups up.
There will be a small marker resembling the D20 item's icon in this room to remind you of the reroll's effect.
Dice Room Three
Think of this room as a vastly upgraded version of the two-pip Dice Room. Stepping onto the die here will reroll every pickup and every trinket on the entire floor. As a result, it's better to use this room when you already know what trinkets are available.
There is a chance that rerolled pickups in shops turn into actual items (passive or active). This room will not, however, reroll any pickups or trinkets currently within Black Markets, Crawl Spaces, Angel Rooms, or Devil Rooms.
The marking in this room to remind you of its effect is a small version of the game's map, signifying that it will affect the entire floor.
Dice Room Four
This room's effect is to reroll every single item pedestal on the floor. This effect is identical to the D6's effect. As with the three-pip room, items in Black Markets, Crawl Spaces, Angel Rooms, and Devil Rooms are ignored.
This room's reminder marker is a small version of the D6's icon.
Dice Room Five
This room's effect is identical to the Forget Me Now item. It will reroll the entire floor completely, and then restart you from the beginning. This room is great for acquiring extra items once you've exhausted the floor and beaten the boss.
When used on an XL floor, the room will restart you at the beginning of the chapter - there is no guarantee that you'll get two XL floors in a row.
The icon for the Forget Me Now is used in this room to remind you of its effect.
Dice Room Six
This room has four effects:
- Rerolls all of Isaac's passive and active items.
- Rerolls all pickups on the floor.
- Rerolls all trinkets on the floor.
- Rerolls all pedestal items on the floor.
This effect simply combines the mechanisms of the first, third, and fourth Dice Rooms.
The symbol to remind you of this room's effect is the icon for the D100, which can do a similar thing when used.