An Etymological Dictionary of the German Language/Annotated/Rose
Rose, feminine, ‘rose,’ from the equivalent Middle High German rôse, Old High German rôsa, feminine; compare the equivalent Dutch roos, Anglo-Saxon rŏse, English rose; adopted in the Old High German period from Latin rŏsa. Had the word been borrowed earlier, the Latin quantity would have been retained in German (in Lilie, from Latin lîlia, the vowel was shortened, because lĭlja was the pronunciation in Middle Latin). Latin *rôsa is, however, implied also by the Romance cognates, Italian rosa and French rose. A Latin ŏ must have led in Old High German to the form *ruosa; compare Old High German scuola, ‘school,’ from Latin scŏla.