The Detolf,if set up properly and gradually adjusted to the full space,would be wonderful for most species(just not great for Syrians,but wonderful for anything else).However as with any cage it does need to be set up just right to keep a robo(or any other hamster for that matter)feeling comfortable otherwise you might assume that it's "too big"
I think the bonus storage with the Detolf on Kallax units is a huge bonus,as you can never have too much storage for random things plus you can potentially eliminate the need for other furniture taking up more space than necessary!
Unfortunately tanks are expensive premade no matter what,and it can be difficult to make your own if you don't know how
Luckily,robos are generally one of the easiest species to house(much easier than a Syrian,at the very least!)with lots of potential choices on the market.