Role Concept not clear

Is there a way to put a User Role check on the Action side?

I’ve read the articles with some “middle” page which checks the user roles. But Isn’t it possible to put the checks via some variable or so? I mean I use now two different security providers and I’m using multiple Login Forms. One which clearly differs from another login page, so the user see’s exactly “HIS” OWN Login page. But I’ll try to put that in one page and maybe use Variable or IF/ELSE conditional showing of fields above the login pages.