I understand that he will gain life back from spellvamp with the use of his rockets and grenade, but does spell vamp also heal from the damage dealt by his turrets?
Heimerdingers H-28G Evolution Turret does not proc spell vamp or on-hit effects.
From what I have heard this is a no. The turrets act as their own separate entity, so you do NOT receive spell vamp.
SOURCE: Mormidon's post on this thread. http://na.leagueoflegends.com/board/showthread.php?t=1099549