Quick Question on Fire SpecFollow

I recently spec fire, and have points into "Torment the Weak", and the same spec as anobix, and that is pretty much standard. So, am i supposed use frostbolts? or how do i "snare" the bosses in raids?!?! or am i just completely wrong?

As stated, multiple people in the raid (especially the tanks) all have an ability that pus up a snare onto the mob (snare being an ability that slows movement speed or attack/cast speed). Thunderclap, infected wounds, etc all count.