Steven Saylor books at Browsers Uncommon Books, updated 26April2012
Roman Blood by Steven Saylor. Mass market paperback.
Author's own page:
Roma Sub Rosa is the title of the series of mystery novels by Steven Saylor set in, and populated by, noteworthy denizens of ancient Rome.
The series is noted for its historical authenticity. The phrase "Roma
Sub Rosa" means, in Latin, "Rome under the rose". If a matter was sub rosa, "under the rose", it meant that such matter was confidential. Continue reading at wikipedia.