Mix all ingredients in a bowl except fresh mint. Adjust seasonings to taste. Top with fresh mint leaves, and, if you like, a sprinkle of ground dried rose petals.
Make ahead: Up to 3 days, covered and chilled (top with fresh mint and dried rose just before serving).
*If your cucumber is especially juicy, replace a few spoonfuls of the yogurt with thicker Greek yogurt. Find dried rose petals at Middle Eastern markets, Latino markets, spice shops, or online. Grind to a powder in a spice grinder before use.