Do you pick first or second?
Since the RBs are trash, you won't be able to improve them without a trade. If you pick first from highest to lowest... Gurley, 1.01 (Fournette), Green, Dez, Thomas, 1.06.
I would guessing 1.06 is the last pick of those. The worst situation is you end up with Gurley, 1.01 and 1.06. Luckily you make the talent cut off at #6 but Cook could be the guy you're left with and he went to a terrible situation for his running style. And Gurley struggled last year and Fournette should be alright but his passing game role is not clear. Which is extremely important in PPR. If you're shaky at RB and don't have good WRs you're going to be bad for awhile.
So is if you have second pick (or whatever equates to having the sixth/last pick at these), I would prioritize 3 WRs available then 1.01, Gurley, 1.06. I put 1.01 over Gurley in this situation because I think the picks trade value (on draft day only!) will be higher. Then you try to move back to 1.03 and take the whoever is remaining of Fournette, Davis and Williams.