I just placed 4 of them against other Routers and was able to insert Uranium Cells into the slots I wanted. I think Routers look for available machines in a certain area and attempt to access them if found.
So now I have Routers inserting items and Import Buses removing spent items.
I believe they look for things connected by tile entities. So if you replaced one of the Routers with a static block, it would no longer connect to the reactor