CREATE TABLE table_18865 ("Result" TEXT, "Date" TEXT, "Race" TEXT, "Venue" TEXT, "Group" TEXT, "Distance" TEXT, "Weight  ( kg ) " TEXT, "Time" TEXT, "Jockey" TEXT, "Winner/2nd" TEXT)

Who was the jockey at Rosehill and the weight was 57.5 kg?
SELECT "Jockey" FROM table_18865 WHERE "Venue" = 'Rosehill' AND "Weight (kg)" = '57.5'
SELECT "Jockey" FROM "table_18865" WHERE "Venue" = 'Rosehill' AND "Weight (kg)" = '57.5'