To make the stuffing, heat a small amount of olive oil over medium heat. Add garlic and sauté until lightly browned; add spinach (working in batches, if necessary), and sauté until wilted. Sprinkle with salt, and set aside.
To make the rolls, mix flour, baking powder, and salt in a bowl. In a separate bowl, combine the spring water and the olive oil. Add the liquids to the flour mixture, and mix with a spoon or with your hands until a ball is formed.
Using a rolling pin, roll a handful of dough into a circle. Top with some spinach and mozzarella slices, and roll up, sealing the seam with your fingers. Continue until all dough is gone.
Lay rolls on a non-stick baking sheet, and bake at 350F until rolls are firm or starting to brown, about 30 minutes.