First of all what is a Roman town or city, there are several types of towns and cities during the Romano British period and each of these types were distinguished by many factors. Below are short descriptions of the types of settlements that were typical during the Romano British period.
Civitas Capital; This is the town from which a tribal canton (civitas) was ruled. The civities was a body of citizens as a political entity called a canton.
Client Kingdom; Client Kingdoms were usually ruled by native chiefs who had become romanised and acted as administrators to these kingdoms. The kingdoms in turn were provided with financial and military support from the Romans, a client kingdom could help stabilise a potentially chaotic region. Chiefs of these kingdoms would sign a declaration that upon his/her death a percentage of the land and wealth would automatically be given to Roman possession, this was partly responsible for the Boudicca uprising, upon the death of her husband.
Colonia; A colonia is a town/city, reserved for retired military veterans. Veterans were granted land, this also meant they assisted in the control of the provinces. In Britain there were at least four known cities? These were Colchester, Gloucester, Lincoln and York. It is possible that Londinium was elevated to a colonia status, but this is not known for definite, as yet there is no archaeological evidence to support this theory.
Municipum; A municipum was a civitas capital, which had been singled out for special treatment. The citizens of a municipum were given the status of “Latin”, which meant they were more than a provincial, but at the same time it didn’t quite carry the same prestige as being a citizen of Rome. Verilanium is certain to have been one of these , but it is not known if there were any other in Britain.
Oppidum; Oppidum is a latin word for town, this was used to describe large native settlements in Britain and Gaul. Camulodunum and Calieva Atrebate both started as oppidums, which eventually became important Roman cities, Camulodunum was eventually raised to the status od a Colonia.
Vicus; A vicus is a small town or settlement which has grown up around a fort; an example of this would the vicus at Bradwell, Nr Brough and Derby in Derbyshire, both of which were a vicus.