I think our ignorance is well founded.

So after 21 posts, has any non Australian found out what a salad roll is, or does no body care?

I don't care much for salad rolls. But Australia produces some of the best vegetarian pies e-vah!

Get with the program, Arbie.
A salad roll is exactly what it says it is. It's a bread roll with salad in it. You can also have a chook salad roll or a ham and salad roll. The variations are limitless. Let your imagination run riot for a bit.

A lobster roll (New England and Long Island: diced lobster meat, onion, celery, maybe lettuce and tomato, mayonnaise, on a sort of hot dog bun) would (if it existed in Australia) be considerede a subclass of salad roll, then?

Well, yes, Vinny it would but under the proviso that it had a couple of portions of sliced beetroot added.
It's obligatory.