I use only "direct contact" stuff like Round-Up for around trees and plants, but not the more powerful "total kill" systemic stuff like Pramitrol.
I use Pramitrol for my oyster shell & bark/pinestraw driveway, for instance, and Round-Up only around trees and plants, being very careful not to let the Round-up get on the tree or plant.
Round-Up will kill the plant that you put it on, and Pramitrol keeps working on roots, seeds, etc. and lasts much longer, usually for the whole season.
As far as Roundup, it needs to be translocated, therefore it has to go onto green vegetation. Once it hits dirt, it locks up with organic soil particles and becomes inert. So in this application, I would say you are pretty safe to use roundup..