hmm, an 06', how old? For now I'll guess 6 months. You're really the rosy expert here, but as for regurgiation, I see three common causes, although there are less common reasons that are possible (impactions, cancer, abscess, birth defects ect.)
Was this animal eating well before? Has it had any other problems?
1)Temperature. Like you said, you keep rosies enough where you know what you're doing. Is there something that might have slipped by? A draft or burnt out heat element... snoop around.
2)Dehydration. The smaller the animal, the more easy dehydration jumps on you. Dehydration is often a symptom of some other medical problem, but itself can also be the sole problem. Is a humid hide available (even desert animals utilize burrows or rock crevices that have a higher humidity)? Remember that 90% of young animals will do fine in husbandry rated a 9 out of 10, but there is that percentage that needs a 10 out of 10. Anywhere you can troubleshoot the need for improvements?
3)You've undoubteably heard of wild caughts = parasites. Parasites can be transmitted to the young before they are born, but it's also likely that intestinal parasites (worms, coccidia, bacteria, amoeba ect) were obtained from the stool released as the female litters.
Whatever the cause, trouble shoot the husbandry as always, and monitor weight loss. A 7% loss in a young animal is time for nutritional intervention (tube feeding or assist feeding). This is of no benefit however, if regurgitation follows. Veterinary care is probably your best bet at this stage.
At home, I'd wait a 10 days without feeding (provided weight loss isn't an issue). Feed the smallest meal accepted. Wait another 7 days or until stool passes and feed another meal of similar or only slightly larger size. Use your judgement. Slowly increase meal size until normal feeding is resumed, but don't surpass one meal per week until you're sure everything is perfect.
Last bit of advice... you can never be to early for a vet appointment, but it's hard to recoup from being a minute too late.
Good luck, you sound like you have an amazing collection 
Ian