Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
rŏsācĕus, a, um, adj. [rosa], made of roses, rose- (Plinian): corona, Plin. 21, 3, 6, § 8: ceratum, id. 24, 13, 73, § 119: oleum, id. 15, 7, 7, § 30.
As subst.: rŏsācĕum, i, n., oil of roses, Plin. 22, 24, 50, § 108; 32, 7, 23, § 68.