I think you'll be fine. But my 2 cents:
Rosie is a mono module. The 2 inputs are mono(both are in the center, not panned left and right). It's designed to let you crossfade between 2 mono signals. You can use the aux send and return to the Clouds to get some stereo reverbs, but you'll be patching back and forth between the Rosie and the Clouds... It's doable, but what if you bought another stereo module one day?
so maybe choose another output module that has stereo inputs(Like the "Outs Mk. II" from Pittsburgh), if you don't want your Clouds' reverb and delays end up in mono.If you want to add something, try some modulation modules(LFO, Envelope, etc).
Yes, the MATHS can be used as a LFO or Envelope, but it's only one module.
Maybe get a LFO to control the size and position of the Clouds?
Cheers! And happy tweaking!