How many rounds were there in Karlskoga Motorstadion with Roger Eriksson at the pole position?
CREATE TABLE "races" (
  "round" real,
  "circuit_location" text,
  "pole_position" text,
  "fastest_lap" text,
  "winning_driver" text,
  "winning_team" text,
  "highest_scoring_team" text,
  "winning_privateer" text
);
SELECT COUNT("round") FROM "races" WHERE "circuit_location"='Karlskoga Motorstadion' AND "pole_position"='Roger Eriksson';