Flora of Melbourne also points to the tubers of some geranium species being used for food
The local (victorian uplands) native geraium species (sorry, I forget the name) is definitly edible.
It has an astringent flavour at first. but then settles to a carbohydrate/starchy flavour.
I taste tested (chewed up and swallowed the whole root) this with an aboriginal friend and my first comment was Jeez you can have this on your own. (Made that puckered up bum face) but once my saliva had washed that astringency away it was ok.
So far we have found quite a lot of basic information about what is edible, but very little detail about what preperation, if any is required.
One has to assume pre settlement populations had only rudimentary cooking impliments which I understand were confined to woven rush baskets used for steaming. No clay pots or metal (obviously). so it would be pretty safe???? to assume most soft foods would have been prepared in this manner. The only case I can think of where extended preparation was required is with cycaids, where repeated rinsing was required.
Another good source of starch in Tassie would be tree fern hearts, the center of Dicksonia antarctica
. This species is protected here in Vic so mind how you go. I have never eaten this or attempted to gather so I know very little about it apart from variouse references stating it was an occasional food source.
I used to know a lot of information about this subject but the older I get the more stuff has to be crammed into my head and i'm afraid its use it or lose it. Forgive me please if some of my comments are a little vague.
Some information comes from personal experience and some from variouse reference books and personal communications.
"Australian carraway" seed may be another to look at. I cant remember (again) the botanical name but it grows higher up in our mountains so may be present in tassie. When it sets seed it forms a horizontal spoked wheel pattern with the seed at the end of each spoke. I've eaten small quantities raw.