form_for only for single-form pages? (ignore previous)

You definitely want the one form to POST to /roles and the other to
POST to /rights, but I'm not sure how that precludes you from using

Perhaps you haven't noticed that a form_for uses a block that has a do
and an end? So you just create the first form with form_for do ...
end and then create the next form with form_for do ... end.

You can have as many forms as you like on a single page.