Chests are more likely to be rerolled into other chests.
The empty chest object that is left behind after opening any kind of chest can be re-rolled into another pickup. As empty chests disappear after leaving a room, it's better to wait until the D20 is full charged before opening chests.
Cannot re-roll pickups into Lil' Battery, but can re-roll pickups into Grab Bags which can contain Lil' Batteries.
Can re-roll pickups into Lil' Battery and other battery pickups, and can re-roll pickups into Grab Bags which can contain Lil' Batteries.
It can re-roll pickups into chests or trinkets and vice versa.
When used to reroll pickups in any shops, pickups may be rerolled into items instead.
Re-rolling pickups duplicated by Rune of Jera, Diplopia and Crooked Penny will result on both the original item and the duplicate being relloled into the exact same pickup.
Golden Trinkets rerolled by D20 will cause the resulting pickup to have the golden effect applied to it. If the trinket is rerolled into another trinket, it will lose the golden effect and act like a normal trinket, otherwise the gold effect will do nothing and will disappear upon leaving and reentering the room.
Additionally, items spawned by chests with the gold effect applied will be golden as well, however other pickups dropped by chests will not be.
Can reroll coins dropped by Tainted Keeper into other pickups, but they will still disappear if not picked up quickly.
Strategy
In Greed mode, the D20 is a one-item game breaker as long as the Shop has a Lil' Battery available. Leave behind as many coins and pickups in the arena as possible. After using the D20, avoid opening chests until the item has been recharged. Avoid collecting things that do not spawn pickups, help buy Lil' Batteries, or help open chests. This can often be repeated indefinitely, leading to collecting coins, bombs, and many pedestal items.
Due to how the D20 interacts with the Book of Virtues, this strategy will not work with Bethany, as using the D20 while playing as her will destroy all pickups in the room.
However, this can be avoided by removing Book of Virtues using Butter!
D infinity can be used for this strategy if it is found.
Safety Scissors: Bombing a Bomb Bum while possessing this trinket will convert the Troll Bombs he spawns into regular Bombs. This process can be repeated indefinitely for unlimited Bomb pickups. These Bomb pickups can then be rerolled with the D20.
Interactions
Book of Virtues: Spawns wisps in the middle ring. In addition to summoning its specific wisp, instead of rerolling pickups, it will destroy all the pickups in the room and has a chance to give a random wisp for each pickup destroyed.
Car Battery: Re-rolls twice instantly without any benefits.
Slightly increases the probability to re-roll into chests.
Options?: Can re-roll both items created by Options?, but only one can still be taken.
Chests are more likely to be rerolled into other chests.
The empty chest object that is left behind after opening any kind of chest can be re-rolled into another pickup. As empty chests disappear after leaving a room, it's better to wait until the D20 is full charged before opening chests.
Lil' Battery, but can re-roll pickups into 
Grab Bags which can contain Lil' Batteries.
Chest and 
Dark Room, the re-rolled chests will always contain items unless they are a 
Red Chest or a 
Wooden Chest.
Shop.
Rune of Jera, 
Diplopia and 
Crooked Penny will result on both the original item and the duplicate being relloled into the exact same pickup.
Golden Trinkets rerolled by D20 will cause the resulting pickup to have the golden effect applied to it. If the trinket is rerolled into another trinket, it will lose the golden effect and act like a normal trinket, otherwise the gold effect will do nothing and will disappear upon leaving and reentering the room.
Tainted Keeper into other pickups, but they will still disappear if not picked up quickly.
Book of Virtues, this strategy will not work with 
Bethany, as using the D20 while playing as her will destroy all pickups in the room.
Butter!
D infinity can be used for this strategy if it is found.
Safety Scissors: Bombing a 
Bomb Bum while possessing this trinket will convert the 
Troll Bombs he spawns into regular 
Bombs. This process can be repeated indefinitely for unlimited 
D20. 
Car Battery: Re-rolls twice instantly without any benefits.
Options?: Can re-roll both items created by 
Dice 
Isaac Unlocks 
??? (Boss) Unlocks 
The Binding of Isaac: Rebirth
