I was concerned about this and discussed it with the guys at Rosco. Its sort of a catch 22 where you attach your wiper. On the front your tires pick it up. If you attach off your 3 point in the rear your tires will knock down the weeds and they will not get wiped. I have been watching the clover in my tractors tracks and it appears the damage from the roundup is minimal.
After your treated the weeds did the tires transfer the glyphosate to the clover? I found out the hard way after I treated the driveway and ran over the lawn.