My experience is exclusively with Mesaba and Pinnacle flights.

On the larger new RJs with FC, the CRJ-900 (frequently coded as CR9), there is space in the bin on one side of the aircraft for normal legal-size (i.e., the 22inch type with 45 linear inches total size that just fit into the sizer) roller bags, but not if they're overstuffed.

However, with the smaller (50 seat?) RJs without FC, the CRJ-200 (coded as CRJ), a roller bag will not fit in the bin unless it is extremely small, about the size of a large brief case. However, the underseat space looks big and there is no divider between the space for the two seats, so that a small roller bag might fit here, especially if it is flexible and you have a nice seatmate. In this case, the large purse would go into the overhead bin so that your stuff doesn't occupy all of your neighbor's space.