Rick, like Egon said, it depends on the soil type, moisture, and type of roots. A few years ago, the place next door to me sold and there were quite a number of cedar trees in the yard, including a row that made a windbreak across the back of the yard that was 10-12' high, and a couple of individual much larger trees. The buyer hated cedar so he hired a guy with a big dozer to uproot all of them. Then he paid me to till the whole back yard and spread several dump truck loads of top soil. That was when I still had the little B7100 and RTS40 Bush Hog tiller. Sometimes the tiller hit roots that made the tiller bounce, and it dug lots of roots of various sizes out of the ground. It did NOT chop up or mulch the roots, but usually just brought them to the surface in pretty large pieces to be picked up. And while it may have seemed to be a little hard on the tiller, it did no damage at all.