Will a rosy boa eat what it regurgitated?

No, any regurgitated meals should be removed immediately, and food and water (unless there are signs of dehydration, in which case you should schedule an appointment with a vet as soon as possible) should be withheld for at least a week, preferably two weeks before trying to feed again. Offer the smallest possible mouse you can find the next time you feed it. Regurgitation is common with Rosy boas but don't be overzealous when trying to get your snake to eat again. You should give it time to build the natural bacteria in its stomach back up to normal levels. Be careful about feeding your snake after it's had a lot of water. This is known to make Rosies regurgitate. Also check your temperature and humidity levels.