On a clean work surface, mound the flour and make a well in the center. Add the egg yolks, olive oil, and salt. Beat the yolks lightly with a fork, then gradually draw in flour from the sides until a dough begins to form. You may not need all the flour. Knead by hand until smooth and elastic, 8 to 10 minutes, adding only a light dusting of flour if the dough feels sticky. Wrap in plastic wrap and refrigerate for 1 hour.

In a mixing bowl, combine the ricotta, feta, basil, and well-drained spinach. Season lightly with salt and black pepper. Stir until evenly blended.

Generously butter the bottom and sides of the baking dish with softened butter. Place the roulade inside. Bake for 40 to 50 minutes, until golden brown on top and firm to the touch.

Let rest for 10 minutes before slicing into thick rounds.