Yup roland's knockback is ignored by elites, but you miss the important part, while they are active they can "tank" the elite, having 2 "tanks" attacking and reciving the damage and using skills and mines will, most likely, make you win, at least that's how i deal with monsters too hard for me to solo.
Having 3 helping hands (Rolands) and making a wise strategy with traps is really helpful.
Having a horde of rolands wont help if you cant survive an aoe attack from elites monster, the best way for sniper is to kiting the mob thats why unmovable rolands are no good. But not all map where the elites camp let you easily to do that.
