When ever your chain gets too out of spec, you will have shifting problems, even on the go, what you are describing if it happens every single time then it could be a problem, the having to role the bike to get it in gear is both common on bigger heavier bikes when clutch is wearing out, and can also be a wearing out clutch on smaller cc bikes with less mileage, and a bunch of other things, it could be anything a person has to look at it in person.... it could be your clutch is getting past its 50 percent life, again it all depends.
how you ride that remaining 50 percent life could go in 5000kms or another 15-20k's, i've seen and myself lasted a clutch for 50k's with constant wheelies, but knowing how to be smoothe is key....learn to be smoothe, maintainance is huge, i check everything on my bike everyday or so. Ask a stunt rider how much you have to maintain a bike to keep it doing what you want it too.
if its just something common like most heavy bikes, you can simply just shift before you come to a complete stop, this problems starts pretty much right after 30 percent life of clutch wear, so unless its gets super annoying, just adjust your chain and clutch line, make sure their good to spec and keep riding, if that doesen't fix your problem. you should find out when the last time the clutch was replaced if its got 25k or higher.
but from experience all the bikes i've tested from 2008 onwards shift smooth like silk, even at stop, the newer the model i noticed the silkier the shift, i tested a 2012 gsxr 600, wow if you flicked it with your toe nail it would shift like a GTR35, newer bikes are like newer cars shift flawlessly, so if the bike is 2012 cbr250, honestly it should not have any hesitation even at a stop, maybe the last owner abused it, or if your the first owner and have racked up miles its simply just got passed its 50 percent clutch life, and is due for a chain adjustment, clutch line adjustment, to match the clutch wear, if the clutch is not already 90 percent life gone, depending of its life abuse or care etc.
In short its a very simple fix needing adjustment or just a common side effect of a clutch reaching its age if everything else is working fine, all in all a very normal thing on bikes, older bikes have this more common, because their mechanics are much more raw, like a 2012 manual civic vs a 1999 civic manual with be a huge diffenrence, but if the newer car is less taken care of it could feel worse then the older one, yet when maintained is feels and shifts better then the old one....hope that makes sense, so since your bike is so new it should not really be having this problem if it is up to date on adjustments and mainatainance.
