I can't find the post where I found it (although you could use search to find it). Here is the copy I made from it though:
(sorry, can't remember who to credit)
For those who have never transferred a roster file via USB drive to your PS3..
Download the file from the link.
Find the zipped folder and unzip it(double click on it and choose EXTRACT TO)...if you don't have a decompression program(Windows does have one built in)....then go here and download the trial version...
www.winzip.com
Extract the contents to your flash drive.
The files will be in this format....PS3(folder)/SAVEDATA(folder)/BCUS944959585(folder and I'm making up the numbers...they will be different)....
Go to the GAME section of your XMB(the screen you see when you start your PS3)...then to the SAVED DATA UTILITY(PS3) section.
Find you USB drive...
Click X...
Hit Triangle and choose COPY and it will copy to your HDD.
LOAD the file when you start your franchise/RTTS
Edit, and one of the stickies in the Roster section has the full minor league as of opening day.