The 21-year-old Toffoli played in 10 regular-season games last season, scoring five points in his first career NHL action. He also appeared in 12 playoff contests, scoring six points while the Kings reached the Western Conference finals.
Pearson appeared in one playoff game for the Kings last season, making his NHL debut. Vey also is among Los Angeles' top prospects, but has yet to play in an NHL game.
The moves leave the Kings with 13 forwards on their roster. Los Angeles opens the regular season Thursday at Minnesota.