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
Cerberus
Anyone know which these two are? I don't.