The overhead bins on Seaborne aircraft are small and will only accommodate small duffle bags, totes, computer bags, small backpacks, etc. as your "personal item". You will have to gate check any standard Roll-aboard carry-ons be it 22" or smaller. If your carry-on bag is slightly larger (because of wheels or bulging side pockets) there's no need to worry since it will be going in the cargo hold, not inside the cabin.