How does roost work?

Question

So I was bored and decided to give showdown a shot. I using my Mega Garchomp team and in a couple battles it was facing off against a Skarmory and Zapdos. I decided to hit them both with a draco meteor and then they used roost. I went first. Since they used roost, I decided to just earthquake them to death but suddenly it said that they're immune. I thought roost removes the flying typing. Am I missing something here?

Answer 1

I went first

Roost restores half of the user's maximum HP.
If a Flying-type Pokémon successfully uses Roost, until the end of the turn, its Flying type is ignored when it is hit by attacks: If the Pokémon has another type, only that type is considered; if the Pokémon is a pure Flying type, all attacks will be normally effective against it.

So you used Earthquake but since you moved first it was immune, then they used Roost after you, Roost only last until the end of the turn. Which made them have a free heal.
Source: Bulbapedia

I've hoped I've helped!

Answer 2

If a Flying-type Pokémon successfully uses Roost, it will now lose its Flying type until the end of the turn.

Source
Roost removes flying type only for that turn on which it is used. Are you sure they are faster than you and used Roost first? Only then you had be able to use Earthquake.

Answer 3

Roost only causes the Pokémon to lose its Flying Type for only 1 turn
So, for example:
Turn 1: You used Draco Meteor
Opponent uses Roost.
Turn 2: You used Earthquake
It’s already Turn 2, not Turn 1, and Roost only caused them to lose their Flying Type in Turn 1, hence they were immune.