To give a full and correct answer:
The move Splash is the only truly useless move, as it literally does nothing.
Rollout will work the same. The Unaware ability only applies when Bidoof uses a move against another Pokemon who has had a stat change.
So if Bidoof uses Defense Curl then Rollout, it gets the defense boost just fine and Rollout doubles in power.
If another Pokemon uses Defense Curl then Rollout against Bidoof, then that Pokemon gets the defense boost just fine and Rollout doubles in power. However, the attacks by Bidoof back at that Pokemon ignore the defense boost.
Regarding Attract, yes it is useless on Mew (and Cryogonal who can also learn it) as it will always fail when used by a genderless Pokemon.
There are plenty of other moves which have very limited use, for example only in double battles. Helping Hand and Quash are useless in single battles.