Quack Grass on Sod Roof

Hey Guys!

So, I'm finishing up my sod roof, preparing to cover 45 mil pond liner with sod, and I'm suddenly feeling nervous about our sod. Particularly, our quack grass. It's ruthless. Most of our root crop veggies come in pierced with it. The junk piles that were left on our property are full of it--I've seen it go through old shoes and recliners. I'm worried it will pierce my pond liner with enough time. Even if I used topsoil (which I can't really, since my pitch is a bit steep), I'm sure it would be there eventually. It gets in anywhere anything is growing.

I've been wondering about putting extra protective layers down now, over the pond liner and before the sod, but I haven't been able to come up with anything that those roots don't get through.

Thoughts? I'm hoping someone can ease my fears or give me ideas.

It looks like they put down some kind of felt over the epdm in this video youtube (Skip to 1:47) Does anyone know what this material is or its purpose?

What did you end up doing with your sod roof?