all of my rosys are very tempermental and usualy do not like it when I change things in their set-ups but I have been using carefresh with them for a couple of years now and it took them a few weeks to get used to it and use it to their advantage, I also bury used paper towel rolls in their bedding and they love to squeeze themselves into them, I think that it makes them feel real secure. if they don't take to the carefresh I would say go back to the aspen.
P.s. how are your sand boas doing?