In a small bowl, whisk egg white with salt and a pinch of sugar until frothy and well blended. Put remaining sugar in a second bowl.
Using a small pastry brush with fine bristles, brush a rose petal all over with a thin, sheer coat of egg white. Working over bowl, sprinkle petal all over with sugar and shake off excess. Set on a fine-mesh cooling rack and repeat with more petals. Every so often, rub your hands together (not over bowl) to remove clumped sugar on them.
Let petals stand uncovered at room temperature until crisp and completely dry, 1 to 2 days.
*If you don't have organic roses in your yard, buy them at a specialty produce store or online.
Make ahead: Up to 1 week, chilled airtight.