Dissolve the yeast and sugar in the lukewarm water. Allow this mixture stand for around 10 to 15 min and you will notice the yeast start to foam.
Meanwhile, sift the salt, xanthan gum and spelt flour together in a bowl. (Sifting helps aerate the flour and results in a lighter dough).
Once the yeast has proved, add the oil, egg and mashed sweet potato.
Gradually add the flour mix and knead dough for around 6-8 minutes until you have a soft, smooth elastic dough. If the dough is still sticky you can add a little more flour. I do find that with spelt flour the dough is a little more soft and sticky than with stoneground but as long as the dough is elastic and forms a ball it still works perfectly.
Place the dough in a lightly greased bowl. Cover the bowl with cling film and place in a warm place until dough has doubled in size or around 1 - 2hours.
Turn the dough out onto a lightly floured surface. Divide the dough into 12 (+/- 100g) equal balls. (Smaller rolls can be made if desired). Roll each piece of dough into a round ball and place onto a baking tray lined with baking paper. Allow the rolls to rise for a further 45 min - 1 hours or until doubled in size.
Combind the egg white and water and then brush this mixtures over the rolls. Sprinkle with sesame seeds and / or poppy seeds if desired.
Bake rolls at 180 degrees celsius (356 degrees F), in a preheated oven until golden brown, about 15 -18 minutes.
Allow to cool and store in an airtight container.