7mmrum,
What kinda "level" are you looking for?
If you don't mind the area gently sloping with the dirt in place, then what highbeam describes should work for ya ...
I'm doing much of the same. I'm placing "cuts" into "fills", and the source dirt has roots rocks, etc mixed in. I'm gettin the resulting grade sloped close with push/pull of the FEL, but nothing close to "level" (i.e. I still has a slope). I'm getting a landscape rake and boxscraper for other needs anyway, and will "finish" the grade to a nice gentle slope when I'm done (aka the fill has settled and is ready for finish this fall).
If you need laser level, then I'd suggest a dozer as others have. If you want a gentle slope, then cut/fill, and rake/boxblade it in ...
Oh, and dig a hole someplace, dump the rock/root debris in it, and cover with the tailings from the hole. Leave a bit of a mound at that point so the debris can settle/decompose.
my 2 penny's