Here is the full list of all 15 Roller Coaster Rampage achievements.
Complete 100 Outside Stunts
Build 50 Loops
Complete 15 Corkscrews
Complete 1 Coaster in Freeride
Achieve 16x Multiplier 16 Times
Receive a Gold Star
Complete a Loop
Perform a Barrel Roll
Unlock All 30 Levels
Collect 1000 Gems
Complete All 30 Levels
Destroy the Seamonster 8 Times
Link 250 Track Sections
Build 100 Complete Coasters
Receive Gold Stars For All 30 Levels