soup? Mugshots? Leftovers? savoury rice/pasta n sauce can be cooked in a thermos full of hot water 20 mins before you want to eat it. potato salad.
And yes, tesco's do a 57g wholemeal roll.
The lunch question comes up on an almost weekly basis so there are loads of threads on the subject. If you do a search you'll find lots of great ideas of what to take.