Heat 1/3 of the butter and add 2/3 of the petals. Stir-fry over medium heat 1–2 minutes. Take out and keep until ready to use at the end.
Soften the shallots in the same pan. Add the rice and stir until the grains get a glossy shine (2-3 min). Add the remaining 1/3 of the roselle, stir for 1 minute, and add a full ladle of hot stock. Let the grains soak up the liquid over medium to high heat, stirring well.
When the liquid is incorporated, add the next ladle. Stirring: I stir every time I add stock, then leave the risotto to gently simmer until the next ladle of liquid, only occasionally stirring. Repeat the process of adding stock and stirring, until the grains have a pleasant bite and are not the least bit chalky. This is probably after about 25 minutes.
When you like the texture of the grains, take the pan off the heat and stir in the ready roselle, the remaining butter and the grated parmesan.
For a naturally sweet touch, top with grilled wild-caught Gulf shrimp, and serve.