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