When to spray a new clover plot

[sailinghudson25]

I rototilled a lawn and made it a clover plot.  About 30% of it survived the tilling.  When should I spray.  Will roundup kill lawn grass.  Not sure if it's fescue or ryegrass.   I got turnips and oats in there.  My guess is theyll die leaving the clover. 

Should I wait until the new clover goes to seed?

I wanted to spray, then overseed some wheat and more clover seed, then sratch it up a bit with the drag harrows.

Reclaiming lawn is new to me.  I'm used to clear cutting, then planting on a lightly weedy site.

I'm using 41% glyphosphate with a 4 gal backpack sprayer

[SplitG2]

if its just grass use clethodium.