Word scarlet, roses are cool.
I hope you are starting with a R. rugosa, or beach rose.
They are generally the hardiest, and the hips that they [as a 'species'- type rose rather than a hybrid] set contain viable seeds.
Some commercial varieties set hips, but I am not sure whether the seeds are sterile as a result of hybridization.
Your Q re: the winter freeze; yes, that should be fine. The refrigeration period is meant to simulate winter.
Let me know what happens!
I'm a lazy bum and buy my roses as just bare rootstocks.