Bronze
According to Zander H. Klawans, coins called the aes grave (heavy bronze) began appearing around the year 300 BCE. The denominations of all early bronze coins contained the prow of a ship on the reverse. The obverse (front) had depictions of gods. The as depicted Janus; the semis, Jupiter; the triens, Minerva; the quadrans, Hercules; the sextans, Mercury; the uncia, Roma.
As: The base bronze coin
Semis: worth 1/2 an as
Triens: worth 1/2 of an as
Quadrans: worth 1/4 of an as
Sextans: worth 1/6 of an as
Uncia: worth 1/12 of an as
Dupondius: worth two asses
Tripondius: worth three asses
Quadrussis: worth four asses
Quincussis: worth five asses
Decussis: worth 10 asses
Follis: introduced by Emperor Diocletian; bronze with a silver wash
Centenionalis: introduced by Emperor Constantine I; bronze with a silver wash
Silver
Francesco Gnecchi states that the first silver coins were struck in 268 BCE. They depicted the goddess Minerva on the obverse and Castor and Pollux (the Dioscuri) with the word Roma on the reverse. Later they depicted the emperors.
Sestertius: the base silver coin; worth 2 1/2 asses
Quinarius: worth two sestertii
Victoriatus: originally used to replace foreign coinage; later worth two sestertii
Denarius: worth four sestertii
Antoninianus: introduced by Emperor Caracalla; worth eight sestertii
Siliqua: introduced by Emperor Constantine I; worth 1/24 of a solidus
Miliarensis: introduced by Emperor Constantine I; worth 1/14 of a solidus
Gold
According to Gnecchi, the first gold coins were struck in 217 BCE. They depicted the god Mars on the obverse and an eagle with the word Roma on the reverse. Later they contained portraits of emperors.
Aureus: the base gold coin; originally worth 20 denarii
Quinarius: cast in silver and gold; both worth two sestertii
Solidus: introduced by Constantine I to replace the aureus; worth one denarius
Semis: worth 1/2denarius or 1/2 solidus
Triens: worth 1/3 denarius