The word "rosaceas" is a plural form of the noun "rosacea" which refers to a chronic skin condition. The spelling of "rosaceas" follows the usual rules for forming plurals in English by adding "-s" at the end of the singular word. The pronunciation of the word is /roʊˈzeɪʃəz/, with emphasis on the second syllable. The phonetic transcription shows that the word is pronounced with a long "o" sound, followed by the "z" and "sh" sounds.