Hi Mariusz, i had the same problem/request with Revolution Slider plugin.
I wanted “editor” role to be able to edit the slider(s).
I took a look at the code and I found this in inc_php/revslider_globals.class.php on line 5
const SHOW_SLIDER_TO = "admin"; //options: admin, editor, author
That’s a constant decalaration inside the GlobalsRevSlider class.
I know – generally speaking – it’s not good to modify code, since if you update plugin you will lose this change, but if you change “admin” to “editor” in that line, your problem should be solved.
My Revolution Slider version is 2.1.4, maybe in next release it will be possible to modify that value using wp-admin UI – maybe you can do it right now too, but I didn’t find where ??