Are glyphosate-treated plant roots reliably dead?

My new place has a teeny tiny town garden entirely occupied by vigorous green alkanet. I've had this before it was a recurring nightmare, so I sprayed it with glyphosate a month ago and it has completely died back.

I'm now making a 6ft x 3ft raised bed for veggies, but I can't get hold of compost/topsoil in the coronavirus lockdown without a car. So I was wondering if it would be safe to use some of my garden soil. It looks like good stuff, but I really don't want to bring in living fragments of alkanet root in case they take over the bed.

Does anyone know if roots can survive glyphosate treatment?

Of course, I could (and may) plant direct to the soil, but there's a steep slope and I am hoping to landscape later this year.

 

I believe its works roots die first which cause the top to wilt and die. Some troublesome plants do need a second treatment or if its knot weed a one to 3 year treatment if not more. I don't come across Alkanet so couldn't say if it need another treatment.

 

Thank-you! Alkanet is related to borage and comfrey, with little blue flowers.