Just pulverized some oats in the grinder to have for some other recipes. Can I use the (maybe lightly toasted first) fresh ground oat flour for th...

I don't see why you couldn't use pulverized (ground) oats instead of whole, rolled oats for this recipe.
However - I would use caution when measuring. The recipe calls for 1 1/4 cups of rolled oats. When you use ground oats, a lot more oats is going to fit in that volumetric measurement. Ideally, you could figure out how much 1 1/4 cups of rolled oats weighs and then use an equivalent weight of the ground oats. That's what I would do, anyway. Otherwise you may end up with some seriously dense cookies that don't hold together well or are very dry.
With a quick google search, I found this conversion for you:
http://www.traditionaloven.com/conversions_of_measures/rolled_oats_measures_converter.html
Looks like 1.25 cups of rolled oats is about 112 grams.