Weed Problems in Legacy Buffalograss

The buffalograss was planted 41 days ago and there are many patches of a thin-bladed grass-like plant that has started growing from dry root-balls that looked innocent enough before we planted. We should have removed all the root-balls before we planted. Here's a photo of the dry root-balls and of a watered root-ball.

(Right) Innocent-looking dry dormant root-balls we left in the soil.
(Left) Grass or Sedge sprouting from a root-ball after we watered the area.

The photo below shows the buffalograss plugs on the right and the weedy grass-like plants on the left. If the root-balls dry out on the weedy grass, the grass dies back. The roots aren't very deep and have little bulbs on the ends.  We think it's a cool-season grass or (sedge?) that we hope we may be able to spray with Roundup when the buffalograss goes dormant after frost. Anyone know what plant this is and how we can get rid of it?

Buffalograss to the Right of Hose.
Weedy Grasses and Field Bindweed on Left.

We think the weedy grasses aren't growing next to our fence because we treat the area frequently with Roundup. If you have time, prepare your soil before planting your buffalograss by watering, spraying weeds with herbicide, watering again, spraying, etc. for at least a few months. It will save you a lot of trouble!

Field Bindweed (wild morning glory) is a big problem in our area and we will really have to fight this weed for a long time.