Hadar's Messenger 4B
Creature - Human Warlock (Common) Circle of Death—5B: Roll a d20. 1-9 | Each opponent loses 2 life. 10-19 | Each opponent loses 2 life and you gain 2 life. 20 | Each opponent loses 2 life, you gain 2 life, and you create two Treasure tokens.
Venom Troll 3GG (number crunch has this between I and L, so there should be another translation for the name)
Creature - Troll (Uncommon) 3G: Roll a d20. Activate only if Venom Troll is in your graveyard. 1-9 | Put Venom Troll on top of your library. 10-19 | Return Venom Troll into your hand. 20 | Put Venom Troll onto the battlefield tapped.
While the UR draft archetype means most dice rolling cards are in blue and red, it doesn't mean the other colors don't have dice rolling too. Here are a bunch of dice rolling mana sinks.