
Digging out is just manual labor. But the first thing that occurred to me is do you know what has been sprayed on the roses in past years? There are many products and you want to know how long each persists in the soil. It isn't necessary to remove all the rose roots but do get the large ones. I would mix several inches of compost and peat in the top 2-3 inches. Plant or sow seeds then mulch with straw, shredded leaves or wood mulch. Tilling is no longer recommended. If you plant on transplanting the roses, this link will help: https://www.gardeningknowhow.com/ornamental/flowers/roses/how-to-transplant-roses-tips-for-transplanting-a-rose-bush.htm