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