Here is the full list of all 12 Rotastic achievements.
Unlock access to world 3 in campaign mode
Complete 5 levels in campaign mode
Do the Rotastic trick
Unlock access to world 5 in campaign mode
Unlock access to world 7 in campaign mode
Get 5 diamond helmets in campaign mode
Collect 5,000 jewels
Get all copper helmets in campaign mode
Kill 3 enemies in 4 seconds in a multiplayer game
Get all gold helmets in campaign mode
Kill 10 enemies in a row without losing a life in a multiplayer game
Play 20 multiplayer games