Williams was an excellent pick because he fills a great need at nose tackle (their starter would be Gabe Watson, who is a mediocre player), and he provides great value at pick 26. Williams has top 20 talent but he often doesn't put a great effort onto the field and all of the teams who picked before the Cardinals either didn't run a 3-4 defense or didn't need a nose tackle. Williams has excellent size, strength, and the potential to be a prototypical 3-4 nose tackle at the NFL level. But he puts up marginal stats and really struggles to keep his weight down.
Washington was an excellent pick here because he could probably immediately fill the void left at inside linebacker after Karlos Dansby's departure for Miami. Washington is more than an ideal fit at 3-4 inside linebacker because, coming into the draft, he was sort of on the border of being a outside linebacker or an inside linebacker in a 4-3 defense. Falling into a 3-4 is perfect because in a 3-4 defense the outside linebackers often blitz. During these plays he provides the versatility to shift from his normal assignment as an inside linebacker to the normal assignment of an outside linebacker (see: Sean Weatherspoon). So he is a perfect fit for the 3-4 defense, and he provides pretty good value at pick 47.
Roberts is a productive player who is among the most NFL ready wide receivers in this year's draft class. At 5'11, he lacks adequate NFL size but he has above average speed and he is among the best route runners of all the players in this year's draft class. He also shows deceptive elusiveness and excellent hands. Solid value at pick 88.
Schoefield is decent value at pick 130, but Schoefield scared/confused me at the NFL combine. During Senior Bowl week, he said he was going to lose weight and try to be a linebacker for once (good), but then he blew out his knee and couldn't play in the Senior Bowl or participate in the NFL combine. Schoefield losing weight was a good idea at the start, for most of his potential is at 3-4 outside linebacker (even though he is pretty raw at that position), but the average weight of a player at that position is around 239. Schoefield showed up at the combine at ... 221lbs? I don't know why he did this, but at this point in his career, Schoefield is a defensive end in a free safety's body. At that weight, Schoefield will not even be an adequate backup at the NFL level.
Skelton was an excellent pick. He has JaMarcus Russell like physical upside and he has put up excellent numbers at Fordham. After watching him in the East West Shrine Game, I could tell that he has the best throw power of anyone I have ever seen (excluding Brett Favre), but he looked very weak minded and he showed no leadership ability on the field. It looked like, now that he was playing against better players, that he was scared out of his mind and he had to compulsively laser every pass until they were too hot to handle for his wide receivers. And he never really communicated with his teammates, never congratulating them for making a nice catch, or yelling at them for dropping his passes. Overall, he doesn't really come across as passionate about the game, but if the Cardinals can really develop him, he could be a great player for years to come. Good value at pick 155.