rockbass belong to the panfish family as far as state regs. go. so most states do not have a size limit on them. as for how many, check with your states regs.. if it says 25 gills in the panfish area, then most likely 25 rockies or a combo of an panfish like, gills, sunnies, rockies and some states like mi. would include crappies in that limit too. but allot of states have their own limits set on crappies, like ohio has a seperate limit for crappies and a no limit on gills except in a few places.
so the bottom line is to check with your state regs. and go from there.