I have had a robo and a Syrian at the same time, twice before (different cages obviously). I preferred this to having two Syrians at the same time, as robos have different needs and sometimes different wake times. Whereas Syrians tend to only want to be out later in the evening or late at night, my first robo used to be out during the afternoon regularly. While he never did get to be fully handtamed, he was quite a communicator and we would sit and have long chats through the open cage door. He would sit for ages listening to me! He did have some playpen time but it wasn't till he was quite old that he was happy to walk into a "taxi" in his cage to be lifted out.
They can be incredibly nervous - that is partly hardwiring because they are so tiny and fragile, and a prey species. All hamsters are prey species but perhaps Robos are more frightened easily than most.
I did find they are good communicators though - with looks and gestures. Eg to let you know if something is wrong. They are still intelligent. My first one once was giving me long hard stares and then running over to the back of the cage and turning his head towards his platform. Eventually I realised the ladder had fallen down and he couldn't get up there.
Cage-wise, they either need to be in a tank style, with solid sides, or, if it's a barred cage, one that isn't too tall and has fairly narrow bar spacing. A larger robo might be ok with 1cm bar spacing. Because if they climb too high and fall they are very easily injured.
