I've housed my robo in the pets at home XL Syrian cage. The bar spacing is 1/4" so no dwarf can get through (in theory). I've since upgraded to the zoozone 2 which is actually a guinea pig cage but I've meshed the top where the bars are to stop my ham getting out.
Whatever cage you chose I'd advise looking at bar spacing. 1/4" or roughly 6mm-7mm is ideal for dwarfs as they can often squeeze through larger spaces of typical Syrian and rat cages which are normally spaced at 1/2" or 1cm
Do you have a budget? Do you have limited space? These are factors which will narrow down your search