I don't believe that I would use anything permanent to cover the rocks up. You may decide to (eventually) hire someone to get rid of them once and for all, and that would simply make it more difficult. But you could certainly spray with RoundUp (active ingredient glyphosate) to kill everything.

Should things continue to emerge after you've applied a healthy layer of chips, it would be easy to do spot spraying.

You can lay down overlapping layers of cardboard to smother weeds & grass (zero dollars expense!).

As rhizo says, don't do anything that would prevent removing the rocks or make it more difficult.

If you can put down some decent garden soil & compost on top of the rocks, you can plant some shallow-rooted things that like dry conditions, since the rocks form a porous "sieve" that will make water drain off very rapidly.

don't know what plants to suggest in your area;
here, I'd go with portulaca, sedum, & smallish yuccas.

Best luck!

You could try offering the rocks on your local CraigsList or Freecycle group. You may just find someone who wants them, and will come and take at least some of them away.