We don't have synonyms for rosett yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are roset, rowett and rosete.
(n) :
Rare spelling of rosette. [(architecture) An element or ornament resembling a rose, especially on a wall or other surface, mostly for decorative purposes.]
(n) :
Rare spelling of rosette. [(architecture) An element or ornament resembling a rose, especially on a wall or other surface, mostly for decorative purposes.]