Here is the full list of all 40 Roundabout achievements.
Honk your horn 500 times, then honk your horn 500 more.
In "Limocide", take out 50 pedestrians.
Purchase every property.
Unlocked the Beary Nice Music Box.
In "Death from Above", survive for 30 seconds.
Unlocked the Multiplier Freezer.
Purchase a pet eagle.
View the "How's Your Driving" screen outside of the DMV ride. Useful, isn't it?
Reach a 35x multiplier.
Die 360 times.
Stand still for a minute of silence at The Memorial.
In "Destruction Derby", take out 8 cars.
Aggressively warn a dozen pedestrians with the Trafffic Coner.
Unlocked the Traffic Coner.
Unlocked the Pickup Finder.
Drove straight for Beth.
Purchase something from The Chrome Dome.
Unlocked the Reverser Wheel.
Make a huge mistake.
Unlocked the Inflatiboat For Cars.
Follow a lady into the big smoke.
Purchase some property.
Collect every star in a single ride.
In "Ball Bouncers", bounce the ball at least 12 times.
Survive the Mountain Fair Demolition Derby without exploding.
Revolve over 53,596 times.
Complete your first eSports Speedrun Challenge.
Get a better eSports Speedrun Time than the No Goblin team.
In "Run Like Crazy", get 150 yards away.
In "Farming Simulator 1977", complete your farming in under 40 seconds.
In "The Great Hunt", find 6 regions.
Collect every Cash Stash.
Accomplish every Sick Jump.
Discover all of the horns.
Purchase every hat and paint job.
Collect every star in every ride.
Reach 100% completion on a mission.
Reach 100% completion for the entire game.
Complete an eSports Speedrun without exploding.
Drive the entire "classic" length of Desert Limo without crashing.