Go to the building's main fuse box and turn off the power for the room where you will install the plaster ceiling rose.
Climb a ladder placed under the area where you will install the plaster ceiling rose. If the light fixture has a a dome, unscrew the bolt at the bottom of it to detach it from the light. Locate the screws or nuts on the outside of the light fixture base and unscrew them to detach the base from the ceiling
Lower the base from the ceiling and locate the wires attached to it. There will be three wires; a white one, a black one and one that is either green or copper colored. Disconnect the wires from the ceiling by unscrewing the plastic cap that connects them to the ones in the ceiling. Set the light aside in a safe location.
Paint the ceiling with a thin layer of PVA bonding with a paint brush. Paint from the opening for the wiring out to 1/2 inch from where the ceiling rose will end.
Paint the back of the plaster ceiling rose with a thin coat of PVA bonding with the paint brush. Allow the PVA bonding to dry completely on both the ceiling rose and the ceiling.
Open a tub of cove adhesive and apply a 1/2 centimeter thick coat to the back of the plaster ceiling rose with a paint brush. If the center of the rose is concave, only apply the adhesive to the higher parts that will come into contact with the ceiling.
Climb the ladder while holding the plaster ceiling rose. Position the center hole of the ceiling rose directly over the hole in the ceiling through which the electrical wires are located. Press the rose firmly onto the ceiling.
Have another person support the ceiling rose while you insert one plaster screw into each side of the ceiling rose with a screwdriver. Insert the screws until they are just under the surface of the plaster. The screws will provide added support for the rose and hold it in place while the glue dries.
Scoop up 1 teaspoon of joint compound with a putty knife and scrape it over the surface of each screw hole to fill them in.
Wait until the joint compound has dried and the sand it smooth with sandpaper until the screw holes are no longer noticeable.
Reinstall the light fixture by reversing the steps taken to remove it. When the light is secured back in the ceiling, turn the power back on at the main fuse box.