All roses were once yellow

It's a bit weird that our base view of some forms of life is the highly selected warped version we've created over centuries. Roses with a single row of petals were the original form, and are still cultivated in many varieties, but don't look like what most of us think of as roses, I guess in the same way that the wild ancestors of many fruits and vegetables don't look like their highly-selectively-bred descendants.

http://www.santaclaritarose.org/Singles.html

Depending on your definition of "rose", this statement is potentially false.

TFA mentions "genus Rosa". If that's the definition, this is false. Wild R. canina is pink:

https://en.wikipedia.org/wiki/Rosa_canina