In a frying pan heat the butter then stir in the flour. Whisk in the milk and bring to a boil. Once boiled, remove from the heat and beat in the egg yolks. Allow to cool then fold into the beaten egg whites. Pour into a Swiss roll tin that has been lined with greaseproof paper then bake at 170 degrees C for 30 minutes.
Turn out onto a tea-towel lined cake rack then quickly roll and allow to cool.
In a bowl combine sour cream, salmon, English spinach and pepper. Unroll the roulade, spread in the sour cream mixture then roll back up. Slice and serve.