[cypher]

Welcome to the forum & congrats on your new robo
Veg of any sort are best introduced gradually so their digestive system can adjust, so a tiny piece finger nail size or a little smaller for a robo once every few days to begin with then you can gradually build up to daily veg.
Try to give a good variety not just one or two things.
If they have the ones with a higher water content they just drink less, they're only likely to get diarrhoea if veg are introduced too quickly.
I've never had a hamster eat more veg than their system can handle, once they've got used to having them I don't tend to worry about quantity tbh, they just eat what they need or want & leave the rest.