Robos require similar size habitat as other species, but just be aware that they are tiny (compared to a Syrian) and are able to squeeze themselves out of quite small gaps so just mind the bar spacing when choosing your cage.
If you are in the UK or Europe, you have much more options than those of us in America.
I personally prefer tanks-style cages as they have great visibility and are very easy to clean and sanitize (I don't move them, I just wipe them down with vinegar solution). As there's no bars, there's also no bar-chewing issues that can cause dental issues in the long run.
Here's a few of my setups for my pairs and groups. Robos love to run, dig, hide, and some also love to climb, so try to arrange your cage so they have opportunities to do these things. Keep in mind that platforms are generally not recommended for pairs+ to avoid territorial problems, but my pairs+ are all fairly settled and the platforms were introduced carefully.
40 gallon breeder tank (36" x 18" x 18") for Smores & girls:
40 gallon breeder tank for Bailey and boys:
Exo Terra Low-Wide Terrarium (36" x 18" x 12") for 3 young girls, no level set up:
Detolf (62" x 16" x 14") set up for group of 4 adult girls:
Sterilite 110 quart bin (31" x 16" x 12") for a pair of boys: