He has no idea how he ended up in bed with Duke Roger. He has no idea why, or what he was thinking, he has no idea where this sudden deep craving for the other mage's presence has come from. Deep in his mind, he might know that Roger isn't simply meeting his eyes to be polite, but that awareness, if he has it at all, will never rise to the level of consciousness.
Eventually, in some twisted, desperate form of self-defense, his mind will interpret the compulsion as love. But for now, all Thom knows is that he is now Roger's, and there was nothing he could do about it.