Wait until beans are up and at the first trifoliate leaf. Roll on a hot day 80 degrees beans will bend but straighten back up the next day. Any broken stems will heal themselves, the tractor tires do more damage than the roller. Don’t roll if the ground is damp mud sticks to roller. I rolled once before planting and a dust storm sandblasted the plants. Spraying and combining is easier to drive. Roll beans as fast as you can drive 11-12 mph.