To determine the identify of this latter-day leader we only need to ask, "Who was it in this dispensation who received the priesthood, the keys of the kingdom and finally the keys of the gathering?" We know exactly who it was. Joseph Smith received the Aaronic Priesthood from the resurrected John the Baptist on May 15, 1829. Then he received the keys of the kingdom as well as the higher Melchizedek Priesthood from the resurrected Peter, James, and John shortly afterwards. This is described in Doctrine and Covenants 13 and 27:12-13. Finally, the keys of the gathering were restored to Joseph Smith by the prophet Moses on April 3, 1836 in the Kirtland temple as described in Doctrine and Covenants 110:11.
“He Shall Set Up an Ensign for the Nations And Shall Assemble the Outcasts of Israel”
Once we realize the true identity of the root, the comments of the Lord concerning him takes on special significance. The Lord said the root will be a descendant of Jesse as well of Joseph who was sold into Egypt. This tells us that Joseph Smith is a descendant of the same Jewish line as King David and the Savior, while his other bloodline was that of the notable Joseph who was sold into Egypt.
We notice in verse 10 that it was a special assignment of the root of Jesse to raise up an ensign to all nations for the purpose of gathering Israel from every part of the world. The Lord also says the Gentiles will be attracted to the "ensign" and many will join the restored Church of Jesus Christ of Latter-day Saints. However, it is interesting that practically all of the Gentiles who have joined the Church have turned out to have a strong strain of the blood of Israel in their ancestry -- usually from the tribe of Joseph.