Make the dough: Dissolve yeast and 1/4 teaspoon sugar in warm water. Stir and let stand until foamy, 5-10 minutes.
Heat the coconut milk, shortening, sugar, and salt in a small saucepan or large measuring cup in the microwave. Don't let it boil, but it should be hot enough to dissolve sugar and salt. Stir and let cool to 110-115°F.
Place the eggs in the bowl of a stand mixer fitted with the paddle attachment. Turn mixer on low and beat eggs for a few seconds. Add the warm milk mixture to the eggs in a slow, steady stream.
Add half of the flour and mix well. Add the proofed yeast to the bowl and mix well. Scrape down the sides of the bowl, if needed. With mixer running on low, add the remaining flour. The dough will be pretty sticky, and that’s fine.
Remove the bowl and paddle from the mixer. Scrape the dough off the paddle and sides of the bowl. Let stand for about 15-20 minutes in a warm place. During this time, the dough will thicken/set up a bit and start to rise.
Sprinkle a little rice flour on a clean surface. Turn dough out onto the flour and sprinkle with a little more rice flour. Pat it into a thick disk. This will help with creating evenly sized rolls. Coating your hands with a little flour each time, divide the dough into 15 evenly sized pieces. You can use a knife, but the dough is very, very sticky, so your hands are a bit easier.
Gently pat the dough and form into balls. Don’t overwork the dough too much or they won't be as light and fluffy after they bake.
Grease a 9x13-inch glass baking dish. Place the rolls in five rows with three rolls in each row. Cover loosely with plastic wrap and let rise for about 45 minutes.
Meanwhile, prepare the coconut syrup. Place coconut milk, sugar, cornstarch (if using), vanilla, and pinch salt in a small saucepan. Bring to a boil and cook for 60 seconds, whisking constantly. Remove from heat and let cool until slightly warm, but not hot. Set aside.
Preheat oven to 400°F. Pour the warm syrup over the raised rolls, allowing some to drip over the top of each rolls. Place pan in oven and bake for 25-30 minutes.
To serve, let cool slightly and serve from the pan or turn them out onto a serving platter, coconut syrup side up.