Gemini says:
"Les routes sont bosselées" is a grammatically correct translation, but it focuses on the shape of the pavement rather than the experience of driving on it.
In French, we usually distinguish between the visual appearance of the road and the physical sensation of the ride.
1. The Best Fit: Cahoteuses (The Sensation)
If you mean the ride is uncomfortable and the car is shaking, this is the most natural word.
"Les routes sont cahoteuses."
- Why: It comes from the word cahot (a jolt or jerk). It perfectly translates “bumpy” when referring to the ride quality.
2. Your Version: Bosselées (The Texture)
If you mean the pavement itself is warped, buckled, or has lumps in it, bosselées works.
"Les routes sont bosselées."
- Why: Bosselé implies a surface covered in bosses (bumps) or dents. It is often used for metal (like a car damaged by hail), but can be used for warped asphalt.
3. The “Pothole” Version (Specific)
If the road is bumpy because it has holes in it, French speakers are very specific:
"La route est pleine de nids-de-poule." (The road is full of potholes—literally “hen’s nests”.)