I do not yet own either bag (but will own the rockie soon!). But I have tried on both bags several times because I have been eyeing both for quite sometime and so anytime I'm in a department store that sells them, I always try them on!
So to answer your question, rocco sits very high as a crossbody (above my hip) and looks awkward because its a bigger bag. I think smaller bags look okay if they are higher up on the body but larger ones just look out of place. Of course this is just my personal opinion!
The rockie sits lower and since it is a smaller bag, looks better crossbody than the rocco. I was actually sold on the rocco until I saw them in person....I didn't even consider the rockie because I thought it would be too small but the rocco is a lot bigger than I thought and because of the weight and the cuteness of the rockie, I decided to go with the rockie.
Good luck!