Some people recommend that when fixing your internal microbiome, you need to eat specific foods to feed your wee beasties. But in a healthy gut, bacterial profiles change over time depending on diet. If I specifically cultivate microbes that eat food x, that might not help me eat food y. Diet consistency matters after introduction of the correct strains more than which particular foods I eat. The human diet is vastly diverse, and for the most part we get along at least well enough to reproduce and have a culture on all of them. I've not yet seen evidence that eating prebiotics leads to better health outcomes, although it's very obvious that replacing pathogenic bacteria with symbiants produces drastic health benefits.
If we're focusing on prebiotics which help us grow probiotics that help us digest prebiotics, are we getting the cart before the horse? Better to cultivate bacteria that love the diet we already eat (or want to eat). Maybe take a consistent quarter of roll each day if you're taking probiotics to improve your wheat tolerance, slowly increasing intake as the microbes take hold?