I was taught that this song was originally from Australia, though I can’t necessarily confirm that.  Of course, when saying each of the actions, you do them.  And hold that action while adding the others.  It’s very similar to twister in terms of the dexterity of some girls to hold the awkward poses and not fall down!  Of course, the addition of the “Tongues Out” was usually left until the end because it was difficult to complete the last chorus

(Chorus)
A roosta sha a roosta sha a roosta sha sha hey
A roosta sha a roosta sha a roosta sha sha hey

The Chorus is repeated, adding a new action
i.e. Thumbs Up
Knees Together
Elbows Back
Chin Up
Bum out
Tongue Out