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.
It seems common enough to me;COD, however, labels the verb ' (to) roster' as 'British'That's possibly the reason.