This is helpful against your issue.

Joke aside, skill in Evade Window to make it easier to dodge away, or block the roar if you use melee, skill in Guard Up to make it more effective, use Guard Point for Charge Blade and retaliate with AED, i'm pretty sure you can do a counter with Long Sword and Lance. And finally, skill in Earplug. It's very helpful fighting against Tigrex as the roar is also damaging, and essential for Brute Tigrex, that thing attack with roar.

I remember in MH2, Khezu will spam roar which take a long time to recover, and when enraged the roaring animation will end sooner than your recovery, so it will roar twice and then zap. It still do that in Rise but at least the recovery are faster.