I have 3 roos with 10 hens. My lead roo made sure the others knew their place and there hasn't been any squabbling since. My lead roo and #2 roo are both Brahmas, light and dark. My #3 roo is a spangled Hamburg, so much smaller than the other two. He doesn't get a lot of lovin' but I have 2 GP Hamburg hens who get his attention. I think the Brahmas know the Hamburg girls are too small because I've never seen anything between them.
I think roo/hen ratios depend a lot on the temperment of your breeds. Brahmas are pretty laid back. My main-man Burt is willing to share with #2 Silas. I'll be adding to my flock in the early spring so I'll even out my ratios too. Also, with larger more docile breeds, like the Brahmas, Cochins, Jersey Giants...they don't need as many so the ratios are smaller. My bigs boys seem to go after the same girls most of the time. More active roos will require more hens.
So, I think !'d learn about the temperments of the breeds involved. The more docil, larger breeds will allow you smaller ratios.