Brandon Jacobs was drafted in the 10th round by the Red Sox in 2009. However, Jacobs has shot up the prospect rankings since then and was ranked as the organization's 7th best prospect before the start of 2012. He was originally picked as mainly an athlete and almost went to Auburn as a running back. With that said, he has below average speed (I timed him at 4.33 to first), which is why he is probably relegated to a corner. So,he is going to have to really hit to make it as a prospect. This year in advanced A Salem, he has been somewhat disappointing in that respect, with a wOBA + of 101. Last year in A-ball, it was an acceptable 118. He has really struggled to hit the ball hard, with a line drive rate of only about 11%. As you would expect with his size (6-1, 225), he has a pretty big swing that looks like it is susceptible to strikeouts (25.4 K% over the last two years seem to support this). His walk percentage is about league average, but he had problems with breaking balls when I saw him.
Randol Rojas was signed in 2008 out of Venezuela by the Texas Rangers. This year, he began the year in class A but was quickly promoted after 12.2 innings. Since joining Myrtle Beach (High A), he has been below average with a 3.96 FIP and 4.46 SIERA.
Rojas' curveball that has good drop and pretty good control. He keeps it low and doesn't really make mistakes with it. He has a lot of confidence in it and it's his feature pitch. However, he doesn't have really good velocity on his fastball. He got in on Brandon Jacobs though and broke his bat. He also has what looks like a changeup with a bit of a drop. He seemed to be able to miss the fat part of the bat and get grounders, which he has in his career (1.40 GO/AO in his career). With that said, he seemed a little too hittable and gave up some hard contact, which he can't do with his low strikeout rate.
Even if the curveball is elite, it is hard to see Rojas being a good pitcher in the Major Leagues. He simply doesn't miss enough bats and doesn't have the fastball. A straight under average right-handed fastball, even with a good curveball, is not something that gets a lot of pitchers to the big leagues.