Preheat oven to 350 degrees F. Butter eight 8-ounce individual souffle dishes, then dust bottom and sides of each with sugar. Place ramekins in the freezer until ready to use.
Combine ½ cup sugar with egg yolks; whisk until pale and thick. Add ricotta, flour, lemon thyme leaves, and salt; mix until well blended.
In a very clean bowl, beat egg whites with an electric mixer until foamy. Add remaining ½ cup sugar and continue mixing until whites have soft peaks. Gently fold egg whites into the ricotta mixture. Divide mixture equally among the ramekins and bake until the souffles have risen and are golden brown, about 40 minutes.
While the souffles are cooking, make the sauce. Combine raspberries, sugar, and water in a small saucepan. Cook over medium heat until raspberries have dissolved, then pass the fruit mixture through a sieve to remove seeds. Serve alongside souffles; your guests can pour the sauce into the center of the souffle at the table.