As with Martin, every Playmobil item I've purchased in the last five years, except for the Viking ship, is a direct result of the Romans.
I'd forgotten about the Roman siege tower, as that was the one Roman set I never purchased due to, in my opinion, its poor design. (I think Playmobil's medieval siege tower, however, is magnificent.) I agree that the Roman siege tower raises a question mark in the series as there is no fortification in the theme to lay siege to. I would have liked to have seen a Roman watchtower instead of that siege tower. Having a few Roman buildings, maybe one or two military and one or two civilian, available, even via DS, would have really been a nice thing for adults. As Martin writes, one could adapt these sets to create a fort and a town. The latter might have brought in the girls, although I agree with Wesley that the knights, pirates, and Romans probably only appeal to boys and they have no interest in domestic items.
Like Martin, I too hold out hope for a Greek and Asian theme or at least a few sets from each theme.
As for the Egyptian pyramid, it's an impressive looking set, but I don't plan on "using" it for anything except as a backdrop for dioramas.