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