I had a rotostak cage for my first hamster, Eddie. It cost me £45 just for the Maxi Mansion!!!!
I was well ripped off. I didnt like the cage that much. It got smelly and dirty too easily because there wasnt that much ventilation and when he went to the toilet, it would go all over the plastic sides and stained the base.
I bought an extension, here it is
but Eddie chewed the food trough, able to sqeeze through an escape! so i had to chuck it out.
When Eddie died (RIP Eddie) I got a new hamster, Lillie. I bought another rotostak extension which was much better, it was called the Cosmo Pod
she loved it.
When Lillie passed away (RIP Lillie) I got another hamster, Kimmi. I kept her in just that cosmo pod until she out grew it so I got her a savic cambridge cage cos she chewed the corner and escaped! little rascal
so i think that if you have a hamster that loves to chew, dont get the rotostak!