I have tried Round Up on Muscari and on Lily of the Valley and in both cases, hand digging worked better.

The herbicide spotted and pitted the foliage but did not kill the bulbs. Even after more than one application.

I wish you luck, I've spent the last 40 years trying to get rid of them. I dig and dig, but they always come back. Sprays do no good, they have waxy leaves and it doesn't penetrate well enough to get the bulb. I usually soak the bed and then pull them out by the handfulls. Of course if you leave only one small baby, they will be right back in a year or two.

Roundup is such an extreme measure. You can also kill things around the object of the spray.
Have you thought about putting up a sign and inviting people to come help themselves to the bulbs right after they have finished blooming?

I would love to have your muscari. I'm creating a 'river' with them in one of my flowerbeds. Be happy to make a swap or for postage.

Peggy