Roman emperors took vows (VOTA) promising to do something for the gods if the gods did something the emperor wanted. The emperor wanted a long reign, of course, and many coin types mention "VOT X"-- vows for ten years of reign.
If the emperor made it to ten years, there would be a ceremony at which the old vows were paid, and new vows taken (SVSCEPTA) for twenty:

Septimius Severus (AD 193-211). Denarius. 19 mm.
VOTA SVSCEPTA XX, the emperor veiled and draped as a priest sacrificing, pouring from a patera over a flaming altar, with legend
RIC 308 "202-210". Sear 6393. BMC 375 "201-210".
Yesterday I posted a large web site on vota coins:
http://augustuscoins.com/ed/VOTA/The main page outlines the subject and illustrates a representative selection of types. Coins that record vows are common and there are too many types to list them. A glance down the main page is probably enough for most readers.
However, it you get interested, there are many links on the main page to related types, many more examples, and related discussions (such as how we date them).
Show us a Roman coin that mentions vows!