WTNY on here will be putting out a roster with all real MILB players, and I would think its getting close, since he did put out a thread with the ETA being real soon and that was close to a week ago, so surely it wont be much longer,lol. With the ratings being redone alog with pitch edits that roster will give you very good sim stats. There will be a good mix of older minor leaguers, and young prospects in this roster as well.
If your wanting MLB and MILB accurate as of opening day, but wont have as manay young prospects due to AAA and AA having accurate rosters, then fairleagueplays here on this site will be the roster for you. Stat wise its also based on ZIPs like the above mentioned, so it will have accurate sim stats thruout your franchise.
If all you care about it having real players, and don't care about having accurate pitcher repertoires and accurate ratings then the OSFM roster by Ridin on here which all SCEA stick ratings is the roster you would probably want.
Just go thru this roster section and you will find roster wise what your looking for. Williards revision roster is just like the 1st 2 I mentioned based on ZIPs projections, and he is the actual original roster editor that started using ZIP projections in rerating the rosters a couple years ago, so obviously his roster is good to use.