Here is a little bit taken from the 65 Roses Day website about the reason for the name.
"65 Roses" comes from the folklore story of a little boy’s effort to pronounce his sister’s condition; Cystic Fibrosis. Instead he called it "65 Roses".
The rose is the national symbol of Cystic Fibrosis. Roses are often considered the ultimate expression of natural beauty, their magnificent bloom and fragrance, juxtaposed on a thorny stem, have captured imaginations for centuries. As a living thing roses can endure harsh conditions, but flourish with care and attention.
Many parallels can be drawn between the rose and a person with CF. The condition Cystic Fibrosis imposes harsh conditions on the lives of those who suffer with it, yet there is a resilience and charm about each person as a result of their struggle and connection with the beauty of life.
For these reasons the red rose has been adopted as the national symbol for Cystic Fibrosis in Australia.
Go here to learn more about it.