Thats interesting about fishmeal and roach. Last two summers but definitely not colder winter temps I have had some good roach fishing with 6mm fishmeal pellets.The only trouble with that groundbait is it is fishmeal and in my view not so good for roach etc,but as you say groundbait is iffy,but if it is the right choice a mug full for a days fishing can get great results...
I have fed a few sparingly until they get going and used a 6mm banded on a 16 B611 or 14 B520 . This was club lakes not heavily stocked commies where they were used to loads of pellets being fed. I certainly sorted the bigger ones.