Melt margarine in medium saucepan on medium. Add green onion. Cook for 3 to 4 minutes, stirring often, until softened.
Add flour. Heat and stir for 1 minute. Slowly add milk while stirring. Heat and stir for about 2 minutes until boiling and thickened. Remove from heat. Add salt and stir.
Beat egg yolks with whisk in large bowl. Add spinach and stir until coated. Slowly add milk mixture to spinach mixture, stirring constantly, until well combined.
Beat egg whites in medium bowl until soft peaks form. Fold into spinach mixture, 1/2 at a time, until no white streaks remain. Spread in greased and parchment paper-lined 10 x 15 inch (25 x 38 cm) jelly roll pan. Bake in 450° F (230° C) oven for 10 to 15 minutes until firm and golden. Run sharp knife along inside edges of pan to loosen. Invert onto large tea towel. Carefully remove and discard wax paper.
Curry Tuna Filling:
Combine all 6 ingredients in medium bowl. Spread evenly over roulade. Roll up, jelly roll-style, from short end, using towel as guide. Wrap in plastic wrap. Chill for at least 4 hours. Cuts into 12 slices.