One of my first small projects after getting a MIG welder was to build a striper for my ZTR mower. Several years ago a made one out of PVC, a wooden dowel and some screws for my push mower. Of course everyone loved it and wanted one. Now that I have a much larger yard and much heavier mower, I had to modify the design a little.
The first thing I wanted this roller to do was to have enough down pressure to really lay the grass down flat, but it also needed to have some flex/spring so I didn't high center the mower and get stuck.
After thinking it through and redesigning it a few times, I ended up attaching the main connection to the lower frame, which is not suspended, this kept it in line with the back wheels and provided a consistent height/level. Then the spring arm ran up to the upper frame which was suspended and wouldn't allow me to high center on the roller and get stuck.
The roller was made from 8 polyurethane rollers with 3/4" inner diameter bearings. The rollers were on clearance for $4 each, which is really what made me start this project.
This is what makes the nice stripes you see in my Husky FEL pictures.