If they are white and can be squashed then they may be slug or snail eggs. Just expose them and let the birds eat them up. I wouldn't disinfect a bed as it will totally destroy the ecology in the soil including worms. Anyway slugs and snails don't really affect roses. If they are newly planted it may also be fertiliser pellets.

Thank you for that. They are not newly planted, but I have just winter pruned them. The "white bits" are exposed so I will have another look tomorrow in the daylight and see if they are squashable!

are they out of the rose stems? if yes it is just the pith. could you post a picture to help us help you better.