Here are 2 rolling bags that will fit in the overhead of any CRJ Delta flies. Neither is too fancy, but I've carried both. Just don't over-stuff them, and always be prepared to debate with the F/A whether it will fit.
http://www.llbean.com/llb/shop/63923?feat=2911-GN2
http://www.llbean.com/llb/shop/63930?feat=2911-GN2
No affiliated with L.L.Bean, just a satisfied customer.