I was watching my son's friends (college freshmen) at five different D2s this year, they were all listed on the spring rosters. One roster had around 30 (private school), and the freshman was playing. One had just under 40 on the roster (fall and spring), freshmen didn't play very much, but were getting some opportunities. Two rosters listed over 50 in the spring, one of those freshmen pitched 1 inning (in 15 games), the other had not played. The last one had over 40 in the fall and spring, son's friend did not seem to be playing. I don't know the individual circumstances of any of these players, nor how much money they got, but the difference in roster numbers was striking, and was publicly available.
For both D2s and mid-major D1s, what's noticeable is not just how many JUCO transfers they have, but how few non-transfer juniors and seniors they have, and whether those guys get playing time. That's also pretty easy to check. In some cases the school will roster 14 freshmen but only 2 seniors who were not transfers.