Over the years we've had several discussions of
roster vs
rota, but the common/rare status of
rostered, and by implication,
rostering, hasn't come up before.
It seems fairly clear that
roster as a verb is more common in Britain than in the US. In fact, the verb isn't even listed in the online Merriam-Webster, or in the American Heritage dictionary. But what's even more striking is how much more often the word
rostered is used in Australia, New Zealand and Ireland than anywhere else. Here is a chart from the Corpus of Global Web-based English, GloWbE:
The pattern is similar in the News on the Web corpus:
So, it's no wonder some of our Australian forumites are astonished the word is not considered common. But it seems it's much less common in a lot of other places.
I think
rostered should remain as rare.