I just returned from an international trip and am jet-lagging badly... got up at 3:00 am this morning and, among other things, ran a Monte Carlo simulation for the 2nd - 4th rounds using PFN's post round 1 rankings.
The MC simulation is not intended to predict who the Cowboys might select. Rather, after a 1000 or so runs, it provides a probalistic view of who might be available.
With that as background,
Second Round (56):
There is <20% probability that either Zach Frazier or Jonathan Brooks will be available
There is >75% probability that one or more of the DTs Orhorhroro, Hall, Jenkins or Fisk will be available.
There is >75% probability one of the inside LBs Gray, Colson or Wallace will be available
Third Round (73 and 87)
There is >75% probability than any 2 of Van Pran, Braylon Allen, Dorlas, Shipley,Trotter, Colson, Sweat, or McMillian (WR) will be available
My take: grab a DT in the 2nd. Take a RB, LB or C in the 3rd.