Rome had no separate priestly caste or class. The highest authority within a community usually sponsored its cults and sacrifices, officiated as its priest and promoted its assistants and acolytes. Specialists from the religious colleges and professionals such as haruspices and oracles were available for consultation. In household cult, the paterfamilias functioned as priest, and members of his familia as acolytes and assistants. Public cults required greater knowledge and expertise. The earliest public priesthoods were probably the flamines (the singular is flamen), attributed to king Numa: the major flamines, dedicated to Jupiter, Mars and Quirinus, were traditionally drawn from patrician families. Twelve lesser flamines were each dedicated to a single deity, whose archaic nature is indicated by the relative obscurity of some. Flamines were constrained by the requirements of ritual purity; Jupiter's flamen in particular had virtually no simultaneous capacity for a political or military career.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): Which member of a family functioned as priest?
paterfamilias