Prepare the baking pan by rubbing a little vegetable oil on the bottom and sides.
Add a good amount of powdered sugar all over the bottom and sides until fully coated. At least 1/8 inch thick of powdered sugar coating.
In a medium saucepan attached with a candy thermometer, add 1/2 cup of water, sugar cup sugar and 1 cup light corn syrup. Bring the mixture to a boil while stirring so it doesn't burn. The sugar needs to be at to 240-250 degrees (soft ball or firm ball) on a candy thermometer. Watch very carefully so it's exactly around 240 to 250 degrees. No less or no more. Once it reaches the temperature, turn the burner to a very low simmer.
In a small bowl, whisk together gelatin and the other 1/2 cup water with a fork. Using an electric mixer, with the whisk attachment and whisk the gelatin so it doesn't clump. Right away, carefully add in the very hot sugar mixture into the mixer while it's whisking.
Beat on high for 10 minutes until thick, fluffy and white. After 10 minutes, add in the rose water extract and salt. Continue to whisk for another minute.
Pour the marshmallow mix into the prepared baking pan. Add the dried rose petals over the gooey marshmallow mixture and then let them sit uncovered for 6-8 hours or overnight.
To remove the marshmallows, cut around the edge of the pan with a well-oiled knife, sprinkled with powdered sugar.
Add powdered sugar to your hands and lift the marshmallows from the pan. Place the marshmallow sheet on a cutting board and cut the marshmallows with the same oiled, powdered sugared knife.