Question

Both move healths you but roost disappears your flying type for a turn so ice, rock and electric types aren't super-effective. However earthquake(an overused move that the most sweepers have got) can hit you...

Answer 1

Use Roost. Even though Earthquake can hit you, Lugia has enough Defense to where it can hold up. And it's not supereffective. But taking the risk to Earthquake is really nothing compared to the three weaknesses that are taken away.

Hope this helps =)

Comments

But Lugia is immune to ground moves.

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During the turn that any Flying-Type Pokemon uses Roost, they lose their Flying -Type attribute for that turn.