In a medium saucepan, combine 2 cups of sugar and 2 cups of water. Bring the mixture to a gentle boil over medium heat and stir until the sugar dissolves completely. Allow it to boil for 5 minutes until it slightly thickens, then remove it from the heat. Pour the syrup into a greased 9x13 rectangular baking pan, carefully coating the bottom.

In a large mixing bowl, sift together the 3 cups of flour, 3 teaspoons of baking powder, 1/2 teaspoon of salt, and 1/3 cup of sugar, mixing well. Cut in 1/2 cup of shortening until the mixture resembles coarse crumbs. Gradually add 1 cup of milk, stirring until just mixed. Turn the dough out onto a floured surface and knead lightly for a few moments to bring it together.

Roll out the biscuit dough into a 12-inch square, about 1/3 inch thick. Brush the surface with 3 tablespoons of melted butter for richness, and evenly spread 3 cups of chopped rhubarb across the top, ensuring it covers the entire area. Starting from one edge, roll the dough tightly like a jelly roll, maintaining the filling inside as you go.

Using a sharp knife, cut the rolled dough into 1 1/2 inch pieces. Place the slices into the prepared syrup in the baking pan, ensuring they’re snugly packed but not overlapping. The syrup should cover the bottom of the pan, ready to soak up into the rolls while baking.

Preheat your oven to 400°F (204°C). Once heated, place the baking pan in the oven and bake for 40 minutes. After the first 10 minutes, carefully baste the rolls with the syrup, ensuring they stay moist and flavorful. They should be golden brown on top and puffed up beautifully when finished baking.

After baking, allow the rhubarb rolls to cool for a few minutes in the pan to let the syrup settle. Serve warm, drizzled with additional basting sauce from the pan if desired. Enjoy these fluffy rhubarb rolls as a delightful breakfast or a comforting dessert.