After the "loss" of Ahman Green, the Packers needed to draft a premier running back. What they ended up with is Brandon Jackson (63rd overall), a smaller (5'-10"), very quick tailback out of Nebraska. Drafting 16th, the Packers knew that both Adrian Peterson and Marshawn Lynch would almost certainly be gone by the time they made their first round pick so they must have spent a great deal of time scouting the next level of running backs. But instead of taking a running back with the their high 2nd round pick, they dropped down 16 places in a trade with the Jets.
Maybe the Packers brass thought the extra 3rd round pick they received in that trade was worthwhile in itself but I don't see how drafting DB Aaron Rouse makes up for dropping 16 places and allowing two more running backs to be taken off the board.
Unless the Packers felt confident that they could drop 16 places and still get a running back they wanted.

He'll need to do better than this to beat out Noah Herron: Packers RB Brandon Jackson
I'm making some guesses here, because I don't know for sure what the Packers were thinking. But considering that the Packers probably have the most wide-open running back by committee situation in fantasy football right now, figuring out if the Packers are happy with Jackson or if he's their Plan C is critically important to fantasy players.
Jackson gets thrown into a pool with Noah Herron, Vernand Morency, P.J. Pope and Arliss Beach. That's a group with a combined total of three NFL starts if you don't have the NFL Guide To Obscure Running Backs handy. The current starter (if you want to call him that) is Morency who showed glimpses of breakaway speed a few times last season but never had the chance to establish himself. He finished with 434 yards on only 96 carries (4.5 avg) and 2 touchdowns.
All four of these guys are about the same size (between 5'-9" and 5'-11", between 210 and 219 lbs) and the same type of speedy, shifty running back so this isn't a case where one of them is favored to see a lot of goal line carries. It's likely that one of the four will perform well in camp, be named the starter by the coaching staff and given the chance to carry the load. If they do poorly in the first two games though, expect to see them get the hook and be replaced by another one of the group. Rinse. Repeat.
So, you'll need to keep an eye on the Packers camp. If Jackson is doing well or has been named the starter early on, I would feel comfortable drafting him as a #3 RB for my fantasy team. If Morency gets traded, cut or injured and the job is essentially handed to Jackson for the season, he could be a viable #2 RB. The Packers offensive line was excellent last season, allowing only 24 sacks and providing enough blocking to let rickety old Ahman Green rush for an average of 4 yards per carry and 5 touchdowns. A full season of Brandon Jackson should provide numbers a little better than that, somewhere around 1100 rushing yards and 6 touchdowns.