CREATE TABLE table_3531 ("English" TEXT, "Japanese" TEXT, "Kana spelling" TEXT, "Revised Hepburn" TEXT, "Kunrei-shiki" TEXT, "Nihon-shiki" TEXT)

how many revised hepburn when english is roman characters
SELECT "Revised Hepburn" FROM table_3531 WHERE "English" = 'Roman characters'
SELECT "Revised Hepburn" FROM "table_3531" WHERE "English" = 'Roman characters'