Detolf looks amazing. Yes maybe fill it up a bit more so less open space but I'm sure you're on with that
Rosie is adorable! I couldn't even see the wheel in the detolf lol. Buried?
With that amount of space she could have two wheels! One in a sand dish at one end like Ria suggested, and another wheel or saucer stood on top of a platform. They like a platform to go under.
Our first robo had both a wheel and a saucer and loved both of them. I've used this 30cm one before - it's ok!
Trixie Running Plastic Disc, 30 cm : Amazon.co.uk: Pet Supplies