Hi Stacey. My last two robos (single hamsters) were housed in my Gabber Rex tank cage, which is basically the same size as a Zoozone 1.
It`s a better space for a speedy robo and you will find it has that extra bit space required for a good wheel and some extras. The Duna Multi is also a nice cage and has the narrow bars on the top grill. Either would do.
The mini Duna has it`s uses, but for a young, active hamster, I feel the minimum size should be around the Zoozone 1 sizing. The mini Duna has had it`s day in terms of size and is still a useful tank to have in case of emergencies or as a spare.
When your new cage arrives, just put everything from the small tank into the new one so as nothing is taken away, like scent. Also try to keep the layout similar unless you really feel it needs changed for the better. You can also incorporate the Duna shelf inside the larger cage as the slits on the shelf should fit between the top and bottom of your multi. You will just need to balance something under the other end to keep it stable like a bendy bridge!
Your robo will love the space! He may seem zooming mad for a bit but leave him to get on with it. He will be running about checking everything out and will eventually find his nest. Your water bottle hole may be high up on this cage, so you may want to look at integrating the bottle inside the cage. I used one of the inserts from a Savic Rody cage, the plastic bit that holds the water bottle? I cut one of those down just to use the water bottle part and slid this between the top and base of my gabber cage and it works a treat. It also means the bottle spout will be nice and low for your wee robo. x