I would go against using the rotastak ladders, when i had my two roborovskis in thsi set up, the ladder fell and trapped my robo in the tube, injuring her eye that luckily healed.
But after that i used fleece lined in the tubes for them to climb up, but you have to make sure they don't chew it!
I foun di wanted a bit more floorspace so i added a bin cage, you may want to consider this in future