People will act like you're an idiot for saying that.
I think I know your post history, and yes you are an idiot.
But not for saying this. Joanna is a striker with very good TDD, and people overestimate the importance of weight classes.
That said, I disagree with you. Joanna relies on reach, which she wouldn't have against Ronda, and she isn't a big 1-punch power striker like Amanda is. She's more of a swarming volume striker. I think she'll have difficulty swarming Rousey, who'll likely utilize her judo and size and strength advantage to take her down from the clinch. Armbar from there. Also, Joanna has fought a lot of rounds recently, and taken a lot of damage. It has to be adding up. I'm a big Joanna Champion fan, but I'll be picking Jessica Andrade to beat her when the time comes.