My Ho-oh in Omega ruby Has 252 evs in speed and atk and 4 in defense, ability is pressure, moveset: Earthquake, Sacred Fire, Brave Bird, and Recover. I have the tm for Roost though and was wondering if it was better than recover for recovery. I know a Pokemon that uses roost loses its flying type and so was wondering if that made roost better or worse for Ho-oh than recover
Recover for Ho-Oh is by far a better choice. Roost means that, for a turn, Ho-Oh is weak to ground types like Landorus or primal Groudon, whereas if you use Recover, that isn't a problem.
Source: Personal experience.
Roost and Recover both has its advantages and its disavantages
Roost: Loses flying typing so its n longer 4x weak to rock, electric is now neutral and ice is not very effective, but ground types can hit it and bug type moves will only be 1/2x not 1/4x.
Recover: Just recovers health, it does nothing else, it can be seen as an advantage and a disadvantage at the same time.