Crazy fish (Ben), I admire your stand but soufflé is right about four robos living together. There is no cast iron guarantee they will stay that way and it might be foolhardy to go head first into this if you have never kept robos before. They are fast and furious little monsters! What you might want to do is get a pair rather than four. A pair are neither likely, nor unlikely to stay forever together either, but your chances will be higher.
What cage have you ordered for them? Robos thrive in tank-style cages like the Zoozone 1 or 2 as they are not climbers but more run around loons that dig! Will the hamsters be solely yours or shared? It`s very important too that they always are together and not lifted out and separated. This alone could cause them to fight. If they have a large enough cage, robos really don`t need play pens or placed in other areas. They love their own space with a fast wheel/wheels to play on.
And importantly, will there be any very young children involved? x