Lucius and Callistus by J.P. Bowie
Raised in the city of Capua, renowned for its gladiator training grounds---Lucius, a young patrician, is unprepared for the obsessive desire that almost overwhelms him when he first sees Callistus, a captive Gaul condemned to a life, and probable death, in the arena. Unsuccessful in his attempt to buy Callistus and save him from a premature death, Lucius instead follows his career, attending all of his bouts in the arena, including one with Spartacus, the rebel slave. Spartacus incites Callistus and his fellow gladiators to rebel and form an unbeatable army, almost bringing the Roman legions to their knees.
Although torn between his love for Callistus and loyalty to his friends and family, Lucius determines that before one, or both of them might die, he must find Callistus, confess his feelings, and spend at least one night in the arms of the man he loves.
This is the prequel to Warrior Prince