Supermarket cages

I'd have thought they would be too open to retain a) heat and b) compost.

But you could separate the four sides and use each as perhaps pea / bean 'netting' for climbing plants etc.

Roller cages?!?  Where are you getting them? 

line them with polysheet and cardboard and they work 

or a bulk  aggregate bag inside would be good.

A quick update . It is now in use on my second plot, lined with cardboard and full!!!!!!!!!!