Preheat the oven to 375° and position a rack in the middle of the oven.
In a medium saucepan, combine 1 cup of the sugar with the water and bring to a boil over moderately high heat. Stir with a wooden spoon to dissolve the sugar. Using a wet pastry brush, wash down any sugar crystals from the side of the pan. Continue to boil the sugar syrup, without stirring, until a golden amber caramel forms, 6 to 8 minutes.
Remove the saucepan from the heat and dip the bottom of the pan in a bowl of cool water to stop the cooking. Immediately pour the hot caramel into eight 4-ounce ramekins; swirl to evenly coat the bottoms with caramel. Set the ramekins in a roasting pan.
In a food processor, combine the ricotta with the whole egg, egg yolks, cream, rum, vanilla, orange-flower water, orange zest and the remaining 1/4 cup sugar. Process until smooth. Pour the mixture into the ramekins. Put the roasting pan in the oven and pour enough hot water into the pan to reach halfway up the sides of the ramekins.
Bake the ricotta custards for about 45 minutes or until golden brown on top and set around the edges but still slightly soft in the center. Transfer the ramekins to a rack and let cool. Cover and refrigerate the custards overnight.
To unmold, run a small knife around each custard, place a dessert plate on top and invert, giving the ramekin a little shake. If the custard sticks, briefly dip the bottom of the ramekin in hot water and invert again.