Roman Coins
This is part of my collection of Roman coins, listed chronologically.

I Republican Rome (to 27 BC) 
IIAugustus to Domitian (27 BC to 96 AD) 
IIINerva to Marcus Aurelius (97 to 180 AD) 
IVCommodus to Trajan Decius (180 to 251 AD) 
VTrebonianus Gallus to Tetricus (251 to 273 AD) 
VIAurelian to Carinus (270 to 285 AD) 
VIIDiocletian to Licinius (284 to 324 AD) 
VIIIConstantine the Great (306 to 337 AD) 
IXConstantine's Heirs (337 to 363 AD) 

Denominations
This history of Roman coin denominations provides a useful explanation of the coins here.
It also shows you how to make change, in case a legionary ever hands you a denarius.