Removing a decorative ceiling rose requires no special tools or expertise, but it will damage the ceiling. Old plaster rosettes or medallions, which are more common terms, were bonded to the ceiling with wet plaster. Newer plastic or foam versions are usually glued with construction adhesive. If the rosette encircles a light fixture, disconnect the electricity at the breaker or fuse box and remove the fixture beforehand. After removing the rosette, repair the plaster or drywall and reinstall the light fixture before turning on the power.
Cut a shallow score, approximately 1/8-inch deep, into the drywall ceiling around the rosette with a utility knife. If the ceiling is plaster, cut or scrape a groove through the plaster and down to the lath around the medallion with the sharp edge of a chisel.
Direct the leading edge of a 3-inch putty knife's blade against the outer edge of the rosette. If the ceiling is drywall, the blade should fit between the medallion and the drywall. If the ceiling is plaster, the blade should fit into the chiseled groove and under the plaster.
Tap the end of the putty knife with a hammer to push the blade under the rosette. Repeat around the perimeter of the rosette, lifting or separating the outer edge. With a plaster ceiling, pry up the underlying plaster to loosen the medallion.
Tap the putty knife handle to force the blade closer toward the center.
Pull down gently on the putty knife handle, prying loose one small portion of the rosette or plaster. Adjust the blade left or right, then pry again. Repeat around the rosette until it is loose enough to pull off.
Grasp the edges of the rosette and pull it off the ceiling.