Instructions
Scroll to "Team Management" and press "X."
Scroll to "Roster Share" and press "X."
Scroll to "Download Roster" and press "X."
Enter the gamertag of the person from which you are downloading the roster using the in-game keyboard. The "X" button selects the highlighted letter or number. Scroll to "Enter" once the gamertag has been entered. Their available roster update will be shown.
Scroll to "Yes" and press "X" to download the roster.
Scroll to "Yes" to save the roster to your PS3 hard drive. Once you start a game, the new roster should automatically be used. If not, scroll to "File Management" and press "X." Scroll to "Load" and press "X." Scroll to the updated roster and press "X" to load it.