Offensive: I'd much rather have Protect than Roost for scouting purposes. It's definitely AC though, but I'd prefer Protect to scout for a stray Ice Beam or HP Ice.
BP: Usually completely outclassed as a BP'er, but Roost fits well on that set so it can have more opportunities to pass off.
SD: Pretty much up to the user, Protect for more versatility and scouting but Roost for recovery faster. I'd slash Protect first.
SubRoost: Lord no, every move is needed on that set.