Rose Cutting?

Rose Cutting?

So in late May I took cuttings from the beautiful old-garden-style rose bush in the yard of the abandoned house next door. I have zero experience with roses (though another OGR I planted this spring seems to be doing well) and am not particularly good with cuttings either, so only one of my four cuttings survived (meaning all its leaves and its stem are still green). I have it in perlite in a cut-down plastic tea jug with plenty of drainage holes, and watering it twice a day seems to keep it happy. My question: How do I know when the root system is well-developed enough to plant the cutting? I can't see through the perlite and I don't want to just rip it out of there to have a look. I'm blessed with great soil and expect it will take off once I get it in the ground, but I don't want to rush things. Thanks in advance for any help you rosarians can offer!
First Spring!

First Spring!

Everything’s growing nicely

Everything’s growing nicely

Masks as Wall Decor

Masks as Wall Decor

Plant ID!

Plant ID!

Narcissus

Narcissus

Hornworm eating my tomatoes!

Hornworm eating my tomatoes!