I feed my roborovski on Burgess Supahamster Harvest mix (not the dwarf version though as it`s bland) I use the normal one with the syrian pictured on the bag.
It has all the flaked grains that the dwarf vesrion lacks, but I remove the extruded biscuits (brown & green) as I don`t like the raising agents and colourants within those).
I add to this:
hemp seed
buckwheat
jumbo organic porridge oats (Tesco`s own brand)
Budgie tonic mix/canary mix (pet shops)
Dry mealworms
I also feed fresh food daily in very small amounts in the form of fresh corn on the cob (one nibblet a day from the cob), two fresh sprouted mung beans (sprouted at home in a jar) and a small piece of apple.
The seperate ingredients can be found in supermarkets, healthfood shops or pet shops.
There are other seeds and wholegrains that can be added but it depends on what you can source and if you feel more variety is required. Robos love small seeds and grains. I wouldn`t touch Harry Hamster for a robo as it`s all large extruded biscuits, corn and alfalfa. Nothing like what a roborovski loves. Which is why I recommend the Burgess Supahamster. Silver`s mixes are obviously the better choice though.