Well, I've located the plates and, indeed, they're clearly Hercules (as a matter of note, I prefer the name "Heracles," but this is a Roman belt, after all. . .).
Clearly depicted are Cerberus (who I prefer to call "Spot"), the Stag, and the Girdle. I don't believe there's enough of the lower-left piece to figure out which one it might be, though since the guy holding the club doesn't appear to be wearing a lion skin, perhaps it's the Nemean Lion (a Labour that would make sense on a soldier's belt).
I can just imagine the feeling of power this soldier must have felt, wearing this belt into battle. It was like he was enacting the mythic drama of Hercules, and I suspect that the belt also reminded him that the duty of being a soldier was not without labour and work, as well, but that even the most basic task could be heroic, if done by the right person. It's a fabulous piece, and I wish more if it were still intact.
I love my library system here at OSU.
The Nemean Lion
The Lernean Hydra
The Cretan Bull
The Belt of Hippolyte
The Apples of Hesperides
Anyone know which these two are? I don't.