hello swingm, i certainly remember you
First off, i feel two robos would be better off with a bigger space in my own opinion( the smaller the space the more likely fights break out)! A robo can live on their own perfectly happy, although its nice for them to have company, like others say a suitable spare cage and prepartion is needed
Chinese hamsters although not strictly solitary, females cannot live together and with males it isn't worth the risk as only rare cases with experienced chinese owners work.
Robos take patience and a calm hand to tame, but once a bond is built they are highley rewarding. Chinese hamsters are also said to be shy.