Its never guaranteed that you can get all roots even with a thin blade shovel or any of the other tools out there.

if you have just a few weeds you can try the digging up method. But if more than a few, either use a selective herbicide or paint on glyphosate for complete kill.

 

something like this ?

 

If you treat it properly, it will kill it all the way to the root. My concern is never about the root; it's more about how many seeds it dropped before I could pull it or kill it.

 

I use something like this

 

I have had good success with this:

https://a.co/d/i141hCi

I got it on Amazon

 

In grass? Only chemicals. In dirt, how about a tiller?