Hi! I have two raised bed planters at my house that the previous owners had vegetable gardens in. I want to use them for the same purpose, but they are overgrown with torpedo grass. The lawn guy sprayed roundup on it, killed a lot of it, but then it started growing back. They are overgrown in that they basically look like an above-ground lawn; it's bad.

I have removed the grass in one bed, but there is an extensive root/runner system in the bed that goes all the way into the ground underneath, through the liner the owners put in (we accidentally ripped through that liner too, while removing it). Although I've removed most of it, there are lots of broken root pieces in the soil so I'm not sure what to do next. Can I salvage the soil? It's full of bugs which I assume is good (gardening is new to me) and it would be a shame to lose such a huge amount of soil and have to pay to replace it. Additionally, what do I do to get rid of the roots beneath the bed, and keep it from growing back once we plant our veggies? If it comes back, is it safe to use roundup on it next to our veggies?

Thanks!!