I think I get it now.
My Cardassians do
roll their r's to varying degrees depending on regional accent, so I guess I tend to imagine them all doing that. The "rh" is always trilled quite strongly (though that's a simultaneous trill/hiss). The "r" is always at least a "tap" like in Spanish, but in certain accents is rolled more strongly in certain positions. Dukat's accent is one that does so quite strongly.