How long does it take for your follower to respawn? Is there any possibilty of your follower NOT respawning? And is there a way to resurrect your follower faster?
I'll assume respawning means the wait time when the follower's health is depleted.
So, I'm afraid you have to wait as I have looked over and over and found no way to make them get back in the fight faster. Takes mine around 10-30 seconds to get back up and start fighting again, although sometimes it does seem to take longer.
I'm now on inferno and always have the Templar with me, and so far he never failed to get back up. Maybe on harder difficulty the respawn time is increased.