Place the yeast, sugar and milk in a bowl and set aside for about 10 minutes until frothy. In a large bowl, stir together the flours, baking powder, xanthan gum and salt.
Mix the oil and egg into the yeast mixture and pour this into the flour mixture, using a fork to bring the mixture together. Tip it out on to a surface dusted lightly with rice flour and knead for 5 minutes, adding a little flour if the mixture becomes sticky. Place in a lightly oiled bowl, cover with a damp cloth and leave to rise in a warm place for about 40 minutes or until well risen.
Roll the dough out on the floured surface into a rectangle approximately 30 x 25 cm (12 x 10 inches). Spread with the passata, then sprinkle over the other fillings. Roll the pizza up from one long edge, then slice into eight pieces.
Arrange the rolled-up pizza scrolls side by side on a lightly oiled heavy baking sheet or tin. They should be pushed up against each other so the sides are touching. Place in a preheated oven, 220°C (425°F), Gas Mark 7, for 12–15 minutes until golden. Eat warm from the oven.