I was wondering if round up would kill the bulbs of these flowers?
Yes, I imagine it would, but it will also kill the surrounding grass too. If you just keep mowing them off each year whenever you start to mow, instead of letting the foliage ripen and wither, they should just fade out on their own pretty much, I would think. Are there too many to dig out?

Sue...digging star of Bethlehem that is everywhere because Round up won't kill it.

have you tried to just over water them???

Why kill them ? Most grass is still dormant when the tulips are blooming so you shouldn't have to mow. If you want to keep them, you can just dig a few groups every once in a while and fill the hole back in with compost/dirt and grass seed.