Prepare the dough. Combine the flour, dry yeast, salt, and sugar in a large bowl. Add the sparkling mineral water and 60 ml of vegetable oil. Mix and knead until a cohesive, pliable dough forms. Add a little more water gradually if needed, as the flour should be fully incorporated without leaving the dough excessively dry.
Make the paste. Mix 60 ml of vegetable oil with 60 g of flour in a separate bowl until smooth.
Roll and fold. Roll the dough into a large sheet. Spread the oil-and-flour paste evenly over the surface, then fold the dough over itself several times to create layers.
Rest the dough. Cover the dough and leave it at room temperature for approximately 1–2 hours, until it is relaxed and easier to roll out. Alternatively, refrigerate it overnight if you prefer to prepare it in advance.
Prepare the pumpkin. Place the grated pumpkin in a pan over low to medium-low heat. Cook, stirring frequently, until softened and some of the excess moisture has evaporated.
Thicken and season the filling. Stir in the semolina and cook briefly. Remove from the heat, add cinnamon and vanilla sugar to taste, and allow the filling to cool.
Shape the rolls. Divide the dough into approximately three portions. Roll each portion into a thin rectangle. Spread the cooled pumpkin filling evenly over the dough, leaving a small border around the edges.
Roll up. Fold the edges inward slightly and roll each sheet into a log. Place the rolls seam-side down on a baking tray lined with baking paper.
Prepare the topping. Mix a little soy milk with 1–2 teaspoons of vegetable oil. Brush a thin layer over each roll.
Bake. Bake in a preheated oven at 180°C (356°F) for approximately 40 minutes, or until the pastry is golden and cooked through.
Cool and serve. Allow the pumpkin rolls to rest for 10–15 minutes before slicing.