I have a copy of The Legacy of Arrius Lurco and some googling for supplemental material turned up two items. A PDF called "Lux in Tenebras" and some sort of "Keeper's PDF" at the following link: The Keeper's PDF. Unfortunately, the entire site appears to be defunct now.
I have since bought a copy of Lux in Tenebras and it has some additional adventures for "Legacy" as well as some unrelated adventures, pre-generated characters and a few handouts about various aspects of Roman society. All the links I can find for the other PDF are dead. Is that material available anywhere? Something I'm wondering is if the the pre-generated characters and the handouts from "Lux" were originally in that Keeper's PDF. I got the impression somewhere that the Keeper's PDF came out before Lux, which makes me wonder if it got folded into the later product.