Robororvskis, robos for short, are the tiniest of the dwarf hamsters, which raises particular problems when selecting a cage for them. Bigger is better for a cage, especially as Robororvskis are social and you should have more than one. On the other hand, it is crucial to find a cage that does not have bars so widely spaced that the hamsters can squeeze out.
The cages specially designed for pet hamsters would seem the obvious choice. Although they are widely available, often second-hand too, and look pretty, they have a few drawbacks. In the case of cages for the larger Syrian hamsters, the bars might be too widely spaced, especially for juvenile Roborovskis. All the cute plastic tunnels, wheels and shelves need cleaning every week, which can become a bit of a nuisance. They also are a slipping hazard for this species. Finally, hamster cages, especially those for dwarf hamsters, tend to be a bit on the small side.
Mouse cages have narrow bars and there isn’t much chance of your hamsters escaping. Such cages are normally pretty small, though. One possible compromise is to have a mouse or dwarf hamster cage for the juvenile hamsters and move them to a larger cage once they mature.
Cages for Other Animals
If you want a big cage, consider those designed for larger animals, again bearing in mind the bar spacing issue. A rat cage, for example, could be an option once your Roborovskis have matured, Baby rats are smaller than adult Roborovski hamsters so some rat cages, although not all, are suitable. Certain ferret and chinchilla cages may also be appropriate, but be careful. If you are not certain whether or not your pet could squeeze out, consider the size of his skull. If he could get his head through, he could escape.
Repurposed aquariums do away with the possibility of the hamsters escaping altogether. It also does not matter if it leaks, because, obviously, you are not going to fill it with water. This means you might be able to pick up a very large plastic or glass aquarium cheaply second-hand simply because it has sprung a leak. Just add a fine wire mesh lid and you have a hamster terrarium. Another advantage is you can include a very deep layer of substrate, which lets the hamsters burrow. The only major drawback of aquariums is that they can become rather stuffy -- it is crucial to clean them out at least once a week and preferably twice.
A second-hand cage must be disinfected before use. Because the fumes from disinfectants can be dangerous to small pets, make sure to rinse the cage thoroughly and wait about a week before transferring the hamsters. Also, the longer you wait, the more chance any exceptionally stubborn bacteria or viruses from the previous inhabitants will have died. There are not many diseases passed between fish and hamsters, so in the case of a second-hand aquarium, you can probably get away with just washing it. Use dishwashing liquid or a vinegar spray, as you would for the weekly cleaning.