O Yeah! Clones are commonly rooted in rockwool and after the roots are seen coming out of the cube they are planted in soil. The plants don't care what the medium is as long as it can: hold some moisture (for nutes) is good draining and allows for growth (assuming that pH is accounted for btw). Coco-fibre, rockwool, peatmoss, clay pellets, gravel. Clones can grow in them all