So, will grass grow back after Roundup? Yes, almost always. You might need to help it along with seed and water. But don't panic if it looks like a war zone for two weeks.
Lawns are forgiving little beasts. They’ve survived my bad decisions—over-fertilizing, scalping with the mower, and that one time I sprayed weed killer during a windstorm and killed my petunias. Your grass will forgive you too.
Now go grab a hose. Your lawn just needs a second chance. And maybe a little therapy.