Just bear in mind that the rodents you feed them often feed on similar materials, so the snake is disposed toward being able to digest plant material even if it doesn't gain much/any nutritional benefit from it (think of it like iceberg lettuce for humans).
If the substrate concerns you due to large/sharp pieces, giving your snake a dry prey item (thawed in water then heated with a blow dryer 'til the fur is fluffy) removes most of the risk, as does "plating" with cardboard. Seen someone on reddit with a cute plastic mat (it's pink with a mouse on it) for their BP.