In a small saucepan, combine the sugar and water and bring to a boil. Reduce the heat to low and simmer for 5–7 minutes until slightly thickened. Stir in the lemon juice and orange blossom water. Remove from the heat and allow the syrup to cool completely.
In a large bowl, combine the walnuts, sugar, and cinnamon until well combined.
Preheat the oven to 350°F. Brush the bottom of a 9x13 pan with melted ghee.
Unroll the phyllo dough and cover it with a lightly damp towel to prevent drying. Place one sheet on a clean work surface and lightly brush with melted ghee.
Sprinkle about 3 tablespoons of the walnut mixture evenly over the sheet, leaving about 3 inches at the top edge and ½ inch on the sides. Fold up the bottom edge by about 1 inch, then roll tightly into a log.
Place the roll seam-side down on the bottom left long-edge of the prepared pan and crinkle so the log reaches about half the length of the pan. Repeat with the remaining phyllo sheets and filling, making two rows of 10. Gently push the ends of each roll inward to create a crinkled effect. Cut each roll into thirds.
Brush the tops of all the rolls generously with the remaining melted ghee. Bake for 35–40 minutes, or until deeply golden and crisp.
Remove the rolls from the oven and immediately pour the cooled syrup evenly over them. Top with crushed pistachios down the center of each row of rolls. Let rest for 1–2 hours to allow the syrup to fully absorb, then serve.