I was doing yard work yesterday and cut several saplings (oak trees I think) that ranges from 1/4 to almost an inch thick. I cut them off as close to the ground as I could (I tried but couldn't pull the roots). The main reason for doing this was because I don't want these to become large trees. That won't go with the rest of the landscaping.

My question is whether there is anything I can or have to do with them to prevent regrowth.

Scott<>

If you have any of the "trunk" part left, where you cut if off, you can purchase "trunk" killer at most all Farm Stores, or possibly Lowe's. If you have an type of Agricultural agent in your local area, they could guide you to a store that handles it.
It comes in various forms, such as liquid, also solid. Some drill a hole in the truck, pour this stuff in. I'm not sure how long it takes, but it will kill the truck, and the roots.
I also have a tree trunk in my back yard, approx. 1 1/2 feet in diameter, and need to get some myself! Small shoots keep coming up from it.
I'm sure you have already done some web research, but here is a link that explains some of it; look under the heading "Tree Trunks".
Kill a Tree | Chemical Tree Control | Forest Herbicide Application
Best of luck.

I work in landscaping and if you can't get the roots of a sapling out try and using a small gardening tool like a scoop to get the roots out. Don't spend money on root killer if you can dig them out.The only time to use root killer is when you have bigger roots that you don't want.