1). Any form of USB storage device is acceptable. This includes all forms of flash/jump drives and iPods.
2). On the actual device create a folder named PS3. Inside of the PS3 folder create a subfolder named SAVEDATA. (Makes is easier to find and easier for the PS3 to recognize).
3). Find the file you wish to download. Download the file and unzip the file to the SAVEDATA folder. It is essential that the file is unzipped prior to copying it onto the PS3.
4). Insert USB device into a USB port on the PS3. Under the Game tab click on Saved Data Utility and find the USB device. Click on it and find the roster file.
5). Press triangle when you have selected the unzipped roster file and go to copy.
You should be all set now. To make sure everything worked, go back to Saved Data Utility and make sure the new file is there.
Sites to download rosters from:
www.psxsports.com
www.maddenmania.com
www.fkrosters.com
PS3 rosters are reported to be out on Friday on both MaddenMania and PSXSports however DT at PSXSports goes through the whole process of reordering depth charts and creating prospects so I would recommend his rosters over the others.