Roisin (Róisín in Irish) is the diminutive of Irish rós, meaning "rose" — so the name means "little rose." Róisín Dubh ("Dark Rosaleen" or "Little Black Rose") is a 16th-century Irish poetic personification of Ireland itself, used in political poetry during times of English rule.
Roisin is among the most popular Irish girl's names. Outside Ireland the unusual spelling (Roisin → ROH-sheen, with silent letters following Irish convention) has limited adoption, but the name is rising.
Roisin reduces to six — the number of small flowering love.