Currently, there are several game systems which require custom dice rolls that can't easily be written in the standard Roll20 dice notation, but which hypothetically COULD be programmed into a rollable table. For example, in Hackmaster, roll 1d100!p, but on a max result, roll 1d20!p, and if that gets a max result, arguably roll 1d6!p. (depending on how you interpret the rules...) You can't program that into the roll20 die algorithm... yet.... but in theory, you COULD make a weighted rollable table which produced a statistically very similiar result to that. However, if you wrote a character sheet which relied on calling such a table, and published it on roll 20, there's no way to link or embed the rollable table you used as part of the sheet: you would have to rely on each GM, individually, to recreate that table themselves, by hand. My suggestion is to fix that: allow for published character sheets to include certain limited rollable tables, as part of the standard template anyone can import.