If they are a big time prospect (first half of round 2 and above) go for it, if not don't touch them until the 6th and make sure that they are extremely gifted in a few aspects(romo has the fastest release in the league and great pocket awareness for example) and that they just need good coaching fundamentals in order to be on par with other teammates.
Big school guys are the safe picks in rounds 3-5 but once you get to round 6 the talent level drops off on those big school guys and their ceiling is significantly lower, so finding a small school prospect that can compete athletically is going to be better for the team because if he can stick then the reward is going to be greater.