I must be the only person who's found Robo's easier to tame than Syrians...
My first Syrian was a grumpy one. He wasn't a biter but screamed everytime I picked him up. As for my current one, it's still early days yet but she'll take food from me and let me stroke her.
The Russians I saw at my local Pets at Home were not nice, one staff member was trying to get one for a customer and I could hear this buzzing noise coming from it. Quite a noise for such a tiny animal. According to her most of the Russians they had in stock at the time were like this.
I did hear that Russians and WW's are harder to tame, but it's not impossible. I've heard that Chinese Hamsters (not technically a dwarf ham but still small) are really nice.
My Robos are pretty tame, but not for sitting and cuddling with as they are like hyperactive children overdosed on sugar! It takes time though as they are quite jumpy when on the move.