when roberts 86' is the scorer what is the round?
CREATE TABLE "table1_28181401_4" (
  "date" text,
  "round" text,
  "opponent" text,
  "result" text,
  "venue" text,
  "scorers" text,
  "attendance" real,
  "match_report" text
);
SELECT "round" FROM "table1_28181401_4" WHERE "scorers"='Roberts 86''';