<font color=red>Oh, I did apply Roundup to the grasses on the land I tilled, but tilled it 4 hours later...maybe it'll work, maybe it won't...I couldn't wait and have lots more roundup</font color=red>
Booo.... hissss.... should have nixed the roundup!! The tiller turns that good ole grass and other green stuff into valuable compost. I don't think that there will any chemical residue with Roundup, but I would definately let the rains flush that soil for awhile. No telling what it could do to anything you may plant in the next few days.
There are a few differing methodologies to tilling. It all depends on soil conditions, moisture, cover crops, etc. For me, I depend upon the depth feet a lot. They prevent the tiller from digging to deep. I till about 3-4" on the first pass. Stop, raise the feet all the way and let the tiller do its job.
Additionally, I till two times. The first pass is to turn under all green manures and accumulated debris - two tilling heights as previously mentioned. I then wait a week or two and till again - usually at full depth. This turns the green manures again to distribute them some more. After that, it's planting time. Except for the deep furrows for potatoes, leeks, and corn.
Terry