[[A Hero's Quest (Gladiator Boy) by David Grimstone|A Hero's Quest]] introduced us to Decimus Rex. This seventh book in the overall ''Gladiator Boy'' series (and start of a new sub-series of 6) begins with our hero, Decimus Rex, and his friends all having received messages from their former ally Teo. I say former because they all thought Teo was dead. They're all hoping against hope that Teo is really alive, but there's a nagging doubt that their nemesis Slavious Doom is setting a trap for them...
It's the Ancient Greeks, rather than Romans, but [[The Beasts in the Jar (Greek Beasts and Heroes) by Lucy Coats and Anthony Lewis]] is superb. For a funny look at gladiator life, check out [[Ditherus Wart: (Accidental) Gladiator (History of Warts) by Alan MacDonald]].