in our case we seed counted cell suspension on 1% solid agarose, when they form spheroids, as they aren't attached to agarose, we easily transfer each spheroid in eppendorf and pipette them until they become cell suspension.
I found some link, maybe it will be useful for you, they separate spheroids from hydrogel system. https://www.youtube.com/watch?v=4A8rrrMkBmc