Judo is about trumping size and strength with skill and leverage.
I don't think Cyborg should want anything to do with Rousey in the clinch or on the ground. Even taking into account her bjj, its probably not worth the risk.
All she really needs to do is kickbox her way to a KO or Decision Iceman style.
I think Ronda has a good chance at taking Cyborg down and beating her. I still think the odds are Cyborg can defend the TD a enough times and get some big shots off and win.
I'm rooting for Rousey.
"I fear no man, but Jim Harrison and Mike Stone are the two last men that I would wish to meet in an alley fight. Jim Harrison's fighting style is not flamboyant or spectacular, it's just simple and deadly!" - Bruce Lee