chelle said:Here's a starter list of what I'd like to try to grow in and around my future rock garden. 
Campanula coriacea
Campanula rotundifolia
Keckiella cordifolia
Lewisia rediviva
Michauxia campanuloides
Mimulus cusickii
Mimulus aurantiacus
Mimulus palmeri
Minuartia laricifolia
Musineon tenuifolium
Nama rothrockii
Penstemon albidus
Penstemon cusickii
Pulsatilla vulgaris
Ramonda myconi
Rhodiola integrifolia
Stachys lavandulifolia
...and lots of others. 
My thoughts....
Unless you've found that you can't grow Campanula rotundifolia in your regular beds, I personally wouldn't tend to use my precious rock garden space for it (and you have indicated that there are lots of other species you're interested in). Yes, it does occur in the lower alpine zone here (through to the prairie grasslands) but it doesn't require any special conditions in my experience (THOUGH with the previous proviso). There are many other exquisite alpine Campanula species that I would save the rock garden space for. Having said that, I haven't yet grown C. coriacea, though Campanula species are a favourite of mine. Take pains to avoid the invasive ones though... Again, with the same line of reasoning, rapid spreaders like C. cochlearifolia and similar are best left in the regular garden.
Rhodiola integrifolia is not much in cultivation so you may have trouble finding plants or seed. Rhodiola species in general though are pretty easy to grow in the rock garden and you may find other species a lot more easily.
I found Stachys lavandulifolia to be too invasive for my tastes. Had it been a lot more freely blooming, I might have felt otherwise, but I yanked it after 2-3 years.
Just my experiences... yours may be different in your area.
