Fry onions and green peppers in butter until tender. Place 2 slices roast beef onto a crepe. Place onions and peppers on top of beef and then roll. Place on cookie sheet. Bake 350° for 15 minutes until hot. Mix sour cream with a little horseradish according to your taste. Swerve beef crepe with spoonful of sour cream mixture on top of crepe.