I don't know how this works, but there occasionally is cross-kickstarter promotions. Which can prove quite effective - for example, Kingdom Death recently plugged the game Myth, and Myth raised like a million dollars. Ok...that was an extreme example.
I was just looking at the youtube comments, and saw that a bunch fell into the "it's too expensive" or "I've got Dungeon Roll" or "Dungeon Roll did this for far cheaper" categories. If Dungeon Roll promoted it on their KS site - he's great with explaining #s and costs, and could show how different Dungeon Dice is from Dungeon Roll - you might get a few more backers. But I don't know the etiquette about initiating this.
Maybe if there were backers of Dungeon Roll, they could message him to make sure he is aware of the game? Or you, as creator of the game, could chat it up with another creator (maybe under the guise of "I also have a dice game and I'm looking for some friendly advice about how to explain the costs of custom injected die molds to potential backers..." and hope he takes a shine to your game?)