Mix the rice flour, powdered sugar, and cardamom together in a small bowl.
In a large bowl or a stand mixer bowl, beat the butter until smooth with a mixer at medium speed.
Beat in the egg and rose water until blended.
With the mixer on low beat in the flour mixture to create a stiff dough.
Remove dough from bowl and place on a floured piece of plastic wrap and with a rolling pin shape the dough into a rectangle 3" wide by ¼" thick. You can also do this with your hands.
If using the dried rose petals - remove individual petals and crush using your hands or do a quick grind in a coffee grinder. You will want about ¼ to ⅓ cup of the rose petals. What you add depends on how much you want on the dough.
Sprinkle the rose petals over the dough and then press the petal into the dough with your hands or the rolling pin so the petals will stick better.
Wrap the dough in the plastic wrap chill for at least 2 hours or overnight.
When ready to bake preheat your oven to 300° F.
Remove dough from plastic wrap and set on a cutting board. Cut the dough in half lengthwise then cut into 24 - ¾" logs.
Transfer the cookies to a parchment-lined baking sheet for 20 - 25 minutes or until the bottoms are golden.
Store the cookies in an airtight container for up to two weeks.