Old English, from Latin Romanus "of Rome, Roman," from Roma "Rome" (see Rome). The adjective is c.1300, from Old French Romain. The Old English adjective was romanisc, which yielded Middle English Romanisshe.
As a type of numeral (usually contrasted to Arabic) it is attested from 1728; as a type of lettering (based on the upright style typical of Roman inscriptions, contrasted to Gothic, or black letter, and italic) it is recorded from 1510s. Roman nose is from 1620s. Roman candle as a type of fireworks is recorded from 1834. Roman Catholic is attested from c.1600, a conciliatory formation from the time of the Spanish Match, replacing Romanist, Romish which by that time had the taint of insult in Protestant England.
"a novel," 1765, from French roman, from Old French romanz (see romance (n.)); roman à clef, novel in which characters represent real persons, literally "novel with a key" (French), first attested in English 1893. And, for those who can't get enough of it, roman policier "a story of police detection" (1928).