Petals are modified leaves that surround the reproductive parts of flowers.
They are often brightly colored or unusually shaped to attract pollinators.
Together, all of the petals of a flower are called a corolla.
Petals are usually accompanied by another set of special leaves called sepals, that collectively form the calyx and lie just beneath the corolla.
When the petals and sepals of a flower are difficult to distinguish, they are collectively called tepals. (source)
So can chinchillas eat rose petals?
Unfortunately they can’t at all. They are not good for chins to eat at all.
For more foods that chinchillas can and can’t eat, check out chinchilla food index