Round up is a contact herbicide and whatever it touches it kills what its labeled for. If you spray it on the disked soil it does nothing. It doesnt keep anything from emerging. It has no residual effect. Wait for a green up then use a burndown herbicide. What I like to do is disk then spray roundup if you didnt totally turn all the grass under. The disk wounds the plant and the up take of roundup is faster causing faster interveinal chlorosis. While at the same time I plant my plot using a the salad bowl effect.
Where the grass is coming up patchy might be because the clover is shading out the grass or that area was disked deeper and the grass is buried.
If i missed anything or not clear dont be afraid to ask