I was surfing through some vertical antenna site for ham radio and I stumbled on some info that suggested that short vertical antennas (ground mounted) do not need radials 1/4 extending from the base, but rather only needed to be in the far field to be effective. An example might be a 18' Hygain that's ground mounted and used on 40 meters. Convention would suggest slighly longer that 34 feet in several directions. However, several radials about 19 feet will work as well.
Now applying that logic, one may conclude that several wires about 10 feet in length should do the job or as long as the antenna is high. So, that being said, I formed a 18" circle using 1/4 inch copper tubing, and soldered 300 ohm twinlead about every inch or so. I twisted and tinned the copper tubing end and then left the far end of the twinlead open, effectivly creating two radials per solder job. So 20 pieces of twinlead is 40 radials. Cheap and easy and it lays flat of the roof with a little help from silicone rubber. The metal ground stakes for camping from Walmart work well if your antenna is mounted on the ground. Just take a paper punch and poke a hole through the center being caeful not to damage the condductor and palnt it in the ground.
The copper circle is connected to the transmitter ground. Your situation may vary slightly.