You bring up some points that I've often wondered about.

What is the lasting impact of round-up in the soil?

Is it safe to till plants that were killed with products like Roundup back into the soil? I ask this considering that it's a systemic that carries the poison from the leaves to the roots to kill the plant, and tilling back into the ground seems like it would kill the roots of everything else planted.

Usually when I want to prep a bed that has grass, I'll either chop out the sod and throw it in a pile to compost, or if it's a raised bed, I'll chop out the sod, flip it upside down in the bottom of the raised bed, the root system makes a great seeding substrate, and it will kill the vast majority of the grass, creating a compost layer for growth. Pretty helpful.

On my small conversion I rented a sod-cutter. It was a lot of work. My new area is pretty big. I didn't think I had the energy for sod-cutting this go-around. I have read that round-up is fairly benign away from water, and you can plant 15 days after application with little if any residual left around. I'm going to give it a week, till it, and then wait another couple weeks to till again and plant. We'll see what happens. My daughter's into peace signs (like all tweens it seems) so this will be a large peace sign garden with mulched walkways making up the internal lines of the sign. Maybe it'll show up on google maps one day.

That would be pretty sweet. There are parts of my back ditch area that I've wanted to overseed with wildflowers, but I'm still fighting off a slew of Nandina, Privet and Asian Wisteria, along with a few nasty, nasty weeds like Bedstraw (Catchweed), Bindweed and some vine with tiny purple flowers, mimosa-like leaves and black, long skinny beans all of which will take over and possibly smother the wildflowers. To boot, it is a runoff creek, and I can't easily use chemicals without risk of contaminating water downstream or the water table.