Some interesting comments here. My two cents: Rojas is by far the best of the bunch defensively and the best all-around player at this point even though he has not hit this season. He is light years ahead of Gregorius and Rodriguez as far as consistency, fundamentals, leadership, and general understanding of the game and his responsibilities in the defense. To me, he is a Janish type player. I would take him on my team any day of the week.
The comparisons of Gregorius and Rodriguez are a bit puzzling because they are not similar players at all. Gregorius is much, much faster. Gregorius has a cannon at shortstop (much better arm than Cozart or Rojas). Gregorius is a very toolsy player but at this point, is a little shaky over the day to day grind (evidence: he had more errors at shortstop by mid June than Rojas had all season last year in the same league). Rodriguez, despite his stolen base total, is an average runner at best (not as fast, for example, as Puckett, who played his position in Dayton in 2009). Rodriguez has made major improvement defensively at second base over the course of this season. Still, he is only what I would term adequate for a low-A second baseman. He does not have the speed to play the outfield. Some scouts feel he is a better fit at third. My biggest problem with him this season is that he struggles with the mental part of the game and struggles to maintain focus for the full nine innings, resulting in costly blunders (although that has gotten better). He is a solid #3 hitter in what is becoming a good Dayton lineup and could possibly end up leading the league in RBI. He has much more pop than Gregorius as a hitter. He is a switch hitter but struggles from the right side of the plate.