In 4.5, Sam is no longer unlocked following the changes made to Galadriel. He is now only present in the Fellowship of the Ring
You can still see his previous roles and abilities below by expanding the page with the button below
Level 1: Seed of the Golden Wood (requires Gifts of Lorien) - Creates a build plot which can be used to make a Mallorn Tree. If the build plot is not used in 2 minutes it will disappear. (Only 3 of these build plots may be used at once)
Sam can receive only one upgrade:
Gifts of Lorien - Galadriel hands gifts from Lothlorien to a hero. The gift can increase the stat of the heroes and/or grants it upgraded abilities. Sam receives Mallorn seeds of the Golden Wood, providing build plots for Lothlórien.
This upgrade can be applied to him through Galadriel's ability Gifts of Lorien.
Sam and Frodo can be used mostly for scouting and supporting. His greatest ability may be Seed of the Golden Wood which provides Mallorn build plots for Lothlórien almost anywhere on the map. To increase his durability on the battlefield you should use his last ability For Frodo.